摘要:

AbstractThe structure and function of the middle ear is considered inGekko gecko(Gekkonidae) andEublepharis macularius(Eublepharidae). Middle ear anatomy is described in detail forGekko, and minor points of difference inEublepharisare indicated. By use of the alternating potentials of the cochlea the peripheral sensitivity function was determined, and then the contribution of the middle ear to this function was assessed by cutting the columellar shaft and removing the more peripheral structures. The sensitivity was then determined by presenting the sounds through a tube sealed over the oval window. This method provides known sound pressures at the columellar footplate and avoids simultaneous stimulation of the cochlea by way of the round window, which other forms of aerial stimulation would produce. This procedure reveals the performance of the middle ear as a mechanical transformer without complicating side effects. The transformer action was indicated as improving peak sensitivity by about 35 db inGekko geckoand by about 53 db inEublepharis macularius.The operation of the middle ear was further analyzed by the use of mechanical vibrations first applied to the surface of the tympanic membrane just over the pars inferior with the ear intact, and then to the stump of the columella after this ossicle was separated. The basic form of the sensitivity function persists in these vibratory types of stimulation, which is taken to mean that this form depends in large measure on the cochlea itself.Two processes are considered as achieving the force amplification required for impedance transformation, which is the principal function of a middle ear. One is a lever action of the columellar system, and the other is the hydraulic action arising from the difference in areas between the surfaces of the tympanic membrane and the columellar footplate. No specific evidence for lever action was obtained in this study. Measurements of areas of the tympanic membrane and columellar footplate indicated fairly large hydraulic ratios in these gekkonoid species. The evidence shows that the efficient transmission of sounds by the middle ear contributes in a significant way to the high degree of auditory sensitivity of these lizards.

ISSN:0022-104X    

DOI:10.1002/jez.1401790102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractThe burrowing squamates of the order Amphisbaenia lack external ears. The middle ear involves an extremely large stapes with the head of its shaft (columellar portion) projecting just posterior to and as far laterally as the quadrate. In most species a cartilaginous extracolumella articulates with the distal tip of the shaft and then stretches along the lower jaw and is attached to the skin in the region of the second infralabial. Records of the electrical potentials of the cochlea in some nine species show sensitivity curves whose maxima are approximately −20dB for a standard output of 0.1 μv. The zone of greatest sensitivity lies in the low frequencies, usually between 300 and 700 Hz. The sensitivity of amphisbaenians differs from that of snakes in being fairly good above levels of 700 Hz, where the latter drops off sharply. Interruption of the extracolumella causes a 20 to 30 dB loss in sensitivity. Sound waves applied asymmetrically produce different electrical responses in the two ears, suggesting an explanation for behavioral observations on the utilization of the syst

ISSN:0022-104X    

DOI:10.1002/jez.1401790103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractMale chaffinches deafened at three months of age produce as adults abnormal calls and subsong. These vocalizations develop as part of a plastic vocal ontogeny which culminates in song learning. In the adult bird, calls and subsong are under the dominant control of the left hypoglossus nerve. Section of this nerve after song crystallization leads to drastic changes in all vocalizations tested. Section of the right hypoglossus results in lesser modifications. These changes are not corrected with practice. When the left hypoglossus is sectioned in young birds before the onset of Spring subsong, the right hypoglossus assumes the dominant vocal role. The food‐begging call of nestlings provides the first evidence in ontogeny for the asymmetrical vocal roles of both halves of the syrinx. This asymmetry of roles is further developed during the vocal stages leading to full song. It is theorized that these vocal stages are of the nature of sequential building blocks, and as such necessary prerequisites for normal song development. The observed ontogeny of hypoglossal dominance can be explained by three assumptions: (1) The left hypoglossus innervates its syringeal musculature before the right one does. (2) This primacy of innervation leads to greater vocal control at the onset of vocal ontogeny. (3) This initial bias is confirmed and further developed as a result of vocal learnin

ISSN:0022-104X    

DOI:10.1002/jez.1401790104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractDistal regions or “marginal ridge” areas of the dorsal mesothoracic disc of mature Drosophila larvae, not previously included in fate maps, were marked by microcauterizationin situ. Structures assumed to have primordia in the distal half of the disc (mesopleura, pteropleura, arch, ventral scutellum, ventral wing hinge and wing proper) are either missing, deficient, or damaged among adults surviving the operation. In contrast, neither the dorsal wing hinge nor mesonotum, which are known to have primordia in the proximal half of the disc, are similarly affected.The pattern of distribution of deformities in surviving adults indicates that (a) the anlage of the mesopleural sclerite is located in the distal edge portion or “marginal ridge” of the disc, (b) anlagen of pteropleura, arch and ventral scutellum may also be tentatively assigned to this location, (c) there are significantly high associations between deformities affecting the pteropleura and the ventral wing hinge, and (d) the anlage of the deep phragma of the postnotum may be more closely related to the first abdominal tergite than to the dorsal mesothoracic disc.The distal localization of pleural, arch, and ventral scutellar anlagen corresponds to the physical separation from mesonotal anlagen predicted from an earlier statistical analysis of genetic mosaics;i.e., these presumptive sclerites are separated from the mesonotal anlagen by the anlagen of the wing in the “pouch” area of the disc.The new information has been incorporated into a hypothetical fate map of the disc, which includes anlagen plans suggested by previ

ISSN:0022-104X    

DOI:10.1002/jez.1401790105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractPortions ofFundulusembryonic shields, usually posterior or anterior halves, were partially dissociated into cell clumps and separate cells by exposure to salt solution lacking magnesium and calcium ions; the dissociates were reaggregated in salt solution containing these ions, then immediately grafted to extraembryonic regions of host gastrulae. Technical difficulties prevented complete dissociation of the shield portions and complete retrieval of the dissociates, but a number of hosts bearing secondary complexes differentiated in association with the grafts developed successfully to late stages.Complexes associated with grafts derived from posterior shield portions frequently formed tails, and differentiated, with few exceptions, the same range of structures described earlier as having differentiated when either unfragmented or mechanically minced shield portions were grafted. In the parts of the new graft complexes remaining attached to the yolksac epithelium, the secondary structures formed were often in topographic disarray, but in the free tails that grew out from these complexes, the axial structures frequently attained normal topographic relationships.Complexes associated with grafts derived from anterior shield portions frequently formed, among other structures, highly differentiated eyes, often with normal retinal stratification, sometimes accompanied by lens, cornea, iris, or optic nerve.The high degree of organization of tails developing in association with grafts of posterior origin, and of eyes in association with grafts of anterior origin, is possibly explicable not by cellular self‐sorting and self‐assembly, but rather by embryonic field phenom

ISSN:0022-104X    

DOI:10.1002/jez.1401790106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractLocalized UV irradiation and protargol staining were used to study the development of cirral primordia during regeneration of the promers ofUrostyla weissei. The aim was to analyze the role of preexisting structures in the formation of primordia.The preexisting frontal cirri were removed by UV irradiation and formation of a new ciliary streaks was observed. When one of the disaggregating old cirri was removed the rest dedifferentiated normally and in the precise place where the irradiated cirrus had been several new kinetosomes appeared. Thus, the formation of these kinetosomes does not depend on the presence of preexisting ciliature at this site. The results provide further support for the hypothesis of integrated cortical activation combined with localized competence of formation sites.

ISSN:0022-104X    

DOI:10.1002/jez.1401790107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractThe initial phases of feather development in the saddle tract of embryonic chick skin were examinedin situandin vitro, under normal and various experimental conditions. A birefringent, fibrous lattice was found in the dermis; it has a strikingly grid‐like organization and is probably collagenous. The development of dermal papillae coincided with a characteristic distribution pattern of dermal cells in relation to this fibrous lattice: elongated cells were aligned along the tracts of the lattice; rounded cells formed clusters at the intersections of the lattice which represented the sites of the future dermal papillae. Evidence is presented that the cell clusters at the lattice intersections are the precursors of the dermal papillae and arise by aggregation of cells that migrate along the fibrous tracts. The results of this study point to a close involvement of the lattice in the formation of the individual condensations of prospective papilla cells and in the patterned distribution of dermal papillae in the dorsal feather field. Experiments with collagenase have shown that the integrity of this lattice is essential for feather morphogenesis. Skin treated with hydrocortisone at the appropriate stages of embryonic development lacks the organized fibrous grid and does not form feathers. The generation of these integumental structures is discussed in the context of epidermal‐dermal interacti

ISSN:0022-104X    

DOI:10.1002/jez.1401790108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractNucleotide substitution that has occurred in the repeated DNA base sequences of several species of galliformes since their origin has been investigated by DNA/DNA hybridization. The results of competition experiments and the thermal stabilities of interspecific DNA/DNA hybrids indicate that a considerable amount of base substitution has occurred between species within the Family Phasianidae. A specific group of genes, the ribosomal RNA cistrons, have been found to be conserved relative to the average DNA base sequences.Gallus domesticusDNA shows considerable base sequence heterogeneity with respect toPhasianus colchicusDNA and is about as divergent from the other members of the Family Phasianidae as are some species outside the family.

ISSN:0022-104X    

DOI:10.1002/jez.1401790109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractThe specific and total activities of acid phosphatase (AcP), hyaluronidase (HU), β‐N‐acetylglucosaminidase (NAG) and lactate dehydrogenase (LDH) of tail fin are constant during prometamorphosis. During climax, as the fin is resorbed, the activities of the hydrolases increase while the specific activity of LDH remains constant and the total activity decreases. The apparent Kmand pH optimum of the hydrolases are the same at prometamorphosis and climax. Similar changes in enzyme activities are found in pieces of prometamorphic fin induced to resorbin vitroby thyroxine treatment. AcP, NAG and LDH are found, but in different proportions, in both fragments of prometamorphic fins separated into epidermis and mesenchymal core. NAG and LDH are more concentrated in the epidermis while AcP is more concentrated in the core. A higher percentage of NAG and AcP activity is found in the mitochondrial‐lysosomal and supernatant subcellular fractions at climax than at prometamorphosis. In addition, the specific activities of these enzymes are higher in the mitochondrial‐lysosomal and supernatant fractions at climax while the specific activity and subcellular distribution of LDH is constant. The increase in activity of the hydrolases of the fin which occurs in synchrony with resorption during spontaneous metamorphosis or that inducedin vitroby thyroxine suggests that these events are related and that the hydrolases are concerned with the degradation of the connective tissues of the fin during re

ISSN:0022-104X    

DOI:10.1002/jez.1401790110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1401790111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY