摘要:

Summary.(1) The aquatic apneustic insects, on hatching from eggs or after each moult, have their tracheal system filled with fluid.(2) A short time after hatching, or moult, the gas suddenly appears, usually in the large tracheal trunks, and thence rapidly spreads into the capillaries.(3) There is no evidence of the secretory origin of this gas, the gas‐secreting cells having never been revealed in insects.(4) The secretory theory of gas does not explain the fate of the disappearing tracheal fluid. Frankenberg's, Pause's and Tillyard's suppositions are discussed and rejected.(5) The following new explanation of the appearance of the gas in the tracheae is proposed:—The tracheal fluid is absorbed by the cells of various tissues from the intracellular capillary tracheoles; the column of the fluid is thus ruptured, the space left by the retiring fluid being immediately filled by gases diffusing from the surrounding media (blood).This supposition explains both the elimination of the tracheal fluid and the appearance of the gas as being due to the same cause—absorption of the tracheal fluid by the tissue

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00534.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.(1) The extrusion of the genital products of echinoids is due to the contraction of muscle fibres in the gonad walls, more abundant in the ovary than in the testis. The contraction of these muscles can be artificially stimulated.(2) A spawning male stimulates ripe individuals of both sexes which are in the neighbourhood to spawn. A spawning female stimulates ripe males to spawn.(3) After spawningStrongylocentrotus lividusre‐forms ripe eggs in nine days at a temperature of 17–

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00535.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.Applying a new method of calculation, it was found that the molecular weights of ten different proteins were in the neighbourhood of 66,700, a figure very much larger than any previous estimates.

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00536.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.The visible changes at the egg surface during early development with or without a fertilisation‐membrane are described. The relation of the substances of the vitelline membrane and of the “gelatinous layer” to the substance to which the extrusion of the fertilisation membrane is due is disc

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00537.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.1. The effects of alterations in the reaction of the medium upon the various changes which succeed the initiation of development in the egg ofSphaerechinus granularisare described. It is concluded that the absence of a visible membrane in eggs fertilised in acid sea‐water is not a secondary result of any of the other known effects of acidity of the medium upon the sperm of the egg.2. If eggs ofSphaerechinusare caused to develop without the formation of a normal fertilisation membrane by any of several methods, membranes cannot be formed by treatment with the usual parthenogenetic agents if more than three or four minutes have elapsed after the initiation of development.3. If eggs in which development has been initiated in this way are placed in water containing small quantities of KCN before the appearance of the gelatinous layer (20–30 minutes after the initiation of development) and treated with sub‐ stances that form membranes in unfertilised eggs, typical membranes are formed. The suggestion is made that the KCN produces this effect by inhibiting the in‐ creased oxidations in the egg.4. It is concluded that the substances which are responsible for the extrusion of the membrane remain unchanged in the surface of these eggs after the initiation of development and therefore play no part in the initiation of development.5. Evidence is brought forward that treatment which can only be external to the egg, namely treatment for 10 secs, with sea‐water acidified topH 4·4 by the addition of HCl, produces the initiation of development in a certain proportion of the eggs.It is concluded that the primary change in the initiation of development must consist of a change of the surface conditions of the egg, while in artificial parthenogenesis membrane‐formation is due to action of the parthenogenetic agent below the surface.6. Evidence is brought forward to show that this primary surface change occurs in parthenogenetic activation when the eggs are placedintothe solution containing the parthenogenetic agent and reasons are given why its effects do not appear in t

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00538.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00539.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.It appears that the Barrington and HaverhillElephasis somewhat distinct from other forms ofantiquusby its higher laminar frequence. As far as is known it was a form with small molar teeth. The fact that there is no great variation in size may be due to the small number of specimens measured but is none the less interesting. The light they throw on the geological level of the beds in which they occur is obscure, but on the whole the period seems to be early rather than late and may be placed provisionally near the top of the Pliocene.The Whittlesea forms appear to be equivalent in their general stage of evolution to those from Clacton, etc. Even in the few specimens discovered there is a wide range of variation in size which would includeausoniusat one end and approach the largest and latest forms ofantiquusat the other. Certain of them however are not unlikeausoniusso that the value of this form as a time mutation appears to be somewhat impaired.

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00540.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.The first lateral leaflet on the left of the mid‐rib of each leaf is measured, and its index breadth/length X 100 calculated.The Leaf Index of a variety must be ascertained from adult leaves on a healthy plant.The younger leaves where the long axis is less than two‐thirds its final length will have a somewhat higher index than the normal.Leaves of secondary growth have, at first, a higher index.Leaves affected with slight mosaic mottling have a reduced index.The variation of the index within any given variety is a normal one and represented by a normal frequency curve.The mean value of the p.e. for one observation when 36 varieties are examined of each of which a minimum of 20 leaves have been measured = 2·36.The p.e. of the difference of two means of 20 each is 74. A difference of two units in the Index may be considered as indicating odds of about 18: 1 against the two varieties being the same, and a difference of 3 units as being almost certain evidence of such distinction, the odds being over 140: 1.Of 65 varieties of which the index was measured, the value of the latter varies between 50 and 72.Neither the place of origin of the seed tubers, nor the locality where the plants are raised have any effect on the Leaf Index, always providing that the plants are healthy.The Leaf Index is a constant for each variety.There is some correlation between early varieties and a low index, and late varieties and a high index.The Leaf Index has given valuable evidence as to the identity of suspected synonymous stocks growing for trial at Orms

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00541.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Thisfungus was considered by Ravn* to inhabit the growing point of its host, like the Smut fungi. That this might well be doubted was pointed out to me by Mr Brooks, who suggested a re‐investigation of the life‐history of this fungus and related forms. The results here summarised make it certain that leaf‐stripe disease of barley is produced without the fungus being present in the growing

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00542.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Inrecent discussions on the geographical distribution of animals and plants the subject has been approached from a novel point of view. An attempt has been made to investigate certain problems of distribution by the statistical or bio‐ metrical method; and it is thought by some that this method may throw new light, not only on the phenomena of distribution, but upon the general principles of biology, of which the facts of distribution must be in some degree the ex‐ pression*. There appear to be certain purely statistical aspects of the problems raised, which have so far been ignored; and since some of these considerations seem to be of a fundamental character, it is perhaps worth while to place them upon record. I advance these considerations with diffidence, because the points which I am about to make are in no way obscure; they are on the contrary very simple; and the only excuse for discussing them is that their fundamental im‐ portance for the statistics of distribution appears to have been overl

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00543.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY