ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00544.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.1. The nucleolus of the oocyte nucleus is at first basiphil, then amphophil and finally completely acidophil showing prominent vacuoles. It discharges into the nucleus deeply basiphil circular and irregular masses of a chromatin‐like substance. The former remain in the nucleus and form secondary nucleoli which, becoming acidophil, ultimately disappear. The irregular masses, the nucleolar extrusions, are first plastered round the nuclear membrane where they bud off small pieces in the cytoplasm. Later they are detached from the nuclear membrane and lie in the cytoplasm where they become amphophil and then acidophil. As a rule they disappear before the vitelline yolk puts in its appearance.2. Strong evidence has been adduced by a comparative study of the various genera of scorpions with and without yolk in the oocytes in favour of the view that nucleolar extrusions are probably concerned in yolk formation.3. The Golgi apparatus in young oocytes consists of small rods collected in a patch on one side of the nucleus. Evidence, both direct and indirect, has been adduced in favour of the view that Golgi rods are transformed into fatty yolk. The Golgi rods, therefore, have a nutritive function in the oocyte ofLithobius.4. The fatty yolk is blackened even by chrome‐osmium, indicating the presence of free unsaturated fat in its constitution. The true vitelline yolk appears a considerable time after the fatty yolk and goes yellowish brown in osmic acid.5. In a centrifuged egg fixed by prolonged osmic acid method the fatty yolk forms a black band at one pole, whereas the vitelline yolk is thrown down at the other pole. The middle area of the egg consists of the mitochondria, the nucleus and the unchanged Golgi rods whose amount is, roughly speaking, inversely proportional to that of the fatty y

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00545.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.Expressions (2·1), (3·1), (4·1), (5·1) are found for the composition of Mendelian populations subjected to partial self‐fertilisation, inbreeding, assortative mating, or selective fertilisation, and equations (2·2), (3·2), (4·2), (5·2) derived for the effect of selection on such populations. The effect of selection is greatly increased by inbreeding and self‐fe

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00546.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.1. Soon after fertilisation the protoplasm at the surface of the egg ofEchinus esculentusis differentiated off from the internal phase of the egg. The egg is thus divisible into two phases, the ectoplasm and the endoplasm.2. Except during the process of cleavage fine processes of endoplasm extend out into the ectoplasm.3. The outer surface of the ectoplasm is of a solid extensible nature. It is not markedly elastic. The underlying portion of the ectoplasm is fluid.4. When cleavage occurs the ectoplasm tends to collect in the segmentation furrow and eventually divides the two portions of endoplasm from each other.5. The normal form of the fully divided cell is due to the pressure exerted on the endoplasm by the ectoplasm.6. The ectoplasm is only stable in the presence of calcium and potassium. It has different osmotic properties to those of the endoplasm. It rapidly shrinks in dilute acids.7. During cleavage the normal form of the cleavage furrow is due to the force exerted by the ectoplasm against the force exerted by the asters.8. The form and extent of the cleavage furrow depend on the position and size of the asters. The asters are capable of deformation by the ectoplasmic pressure.9. Evidence is presented to show that the growth of the two asters must lead to a redistribution of the different phases of the protoplasm (peripheral endoplasm, and ectoplasm), such as is actually observed. Further, the final result of the enlargement of the asters must lead mechanically to normal cleavage. There are, thus, two essentials for cleavage, (i) the cell must be differentiated into two immiscible layers, ectoplasm and endoplasm, (ii) the cell must contain sufficiently large asters to bring about a redistribution of the endoplasm round these two centres.10. The variations in the types of cleavage characteristic of other animal cells can be brought about in Echinoderm eggs by varying either the extent of the force exerted by the ectoplasm, or by varying the size or position of the two asters.11. Cell‐division in Echinoderm eggs is the direct result of the asters reaching a critical size.In conclusion, I wish to express my gratitude to Mr R. Elmhurst, Director of the Marine Station, Millport, N.B., for providing me with facilities at Millport, and for his unfailing assistance in maintaining a constant supply of material during the period 1921

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00547.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.1. In a pond in which Spirostomum occurred in vast quantities thepH of the water was 7·4, that of an aquarium in which Spirostomum were present in large numbers was 7·5, and that of the water containing flourishing cultures of Spirostomum was 7·4 to 7·6.2. The Spirostomum showed the greatest activity in solutions ofpH 7·4. Below this value the activity is reduced, but down topH 6·0 at any rate the effect is not lethal. In solutions abovepH 7·6 to 7·8 the Spirostomum are killed within a few hours if thepH greatly exceeds these values, and in a longer time if they are barely exceeded. In dying as result of the alkalinity of the water being too great the animals assumed a characteristic pear‐shaped malformation.3. Pütter (1903) supposed that the death of Spirostomum which occurred when the animals were placed in shallow vessels exposed to the atmosphere was due to oxygen poisoning. This is shown not to be the case but to be due to thepH rising above the lethal value.4. Spirostomum, when placed in tubes in which thepH of the water at one end is 8·0 and 6·8 at the other, are found to migrate rapidly into the water ofpH 6·8 and then finally settle in the middle of the tube where the water ispH 7·4. This preference for water of a particularpH, which is stronger in its effects than those of light and gravity, disappears in the darkness.5. The normal behaviour of Spirostomum in the aquarium, in the pond and in the collecting jars may be explained to a large extent by the preference for water of a particularpH and by the presence or absence of a verticalpH gradient.6. No evidence was found to connect an epidemic of conjugation with thepH of the water.7. The temperature at which the experiments were performed or the observations made varied from 9 to 15· Centigrade, but the temperature was uniform throughout any tube or jar at the time it was observed. There was no tempe

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00548.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY

摘要:

Summary.1. Chlorocruorin, the red‐green pigment dissolved in the blood of certain polychaetes, exists in an oxidised and a reduced form, which have different absorption spectra. Chlorocruorin is a respiratory pigment in that the oxidised form can be reduced (a) by a vacuum, and (b) by living tissue, and then reoxidised by air.2. Blood ofSpirographis, containing chlorocruorin, gives off on the addition of potassium ferricyanide one‐third of the volume of gas given off by my own blood.3. The absorption bands of oxychlorocruorin and reduced chlorocruorin resemble those of oxy‐ and reduced haemoglobin shifted towards the red end of the spectrum.4. The oxychlorocruorin spectrum differs from that of oxyhaemoglobin in the relative heights of theaand β bands and in the presence of a third much smaller band.5. Reduced chlorocruorin resembles the reduced haemoglobin ofArenicolain that the spectrum varies with the reducing agent employed.6. The band of reduced chlorocruorin has a summit with a buttress on either side. Thus it differs from the simple summit of the mammalian and the double apex of the Arenicolan haemoglobin band.7. The spectra of metachlorocruorin and chlorocruorohaematin differ considerably from those of methaemoglobin and haematin.8. Chlorocruorochromogen closely resembles haemochromogen spectroscopic‐ally. The bands of the former are further towards the red than those of the latter, but the shift is less than in the case of oxy‐ and reduced chlorocruorin relative to oxy‐ and reduced haemoglobin.9. The porphyrin prepared from chlorocruorin is either identical with haemato‐porphyrin or very closely resembles the latter.10. Chlorocruoroporphyrin, like haematoporphyrin, has a brilliant re

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1924.tb00549.x

出版商:Blackwell Publishing Ltd    

年代:1924

数据来源: WILEY