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Part III. — Sixteenth Annical Report 



bodies in the cytoplasm.* He represents in a series of figures the 

 appearances he found in sections of the young eggs, which show in most 

 cases the eliminated chromatic substance in the form of threads connected 

 with the chromatin within the germinal vesicle. He had previously 

 given an account of the vitelline body in the demersal eggs of several 

 species. t In 1893 HenneguyJ described the occurrence of the vitelline 

 nucleus in the eggs of a number of osseous fishes belonging chiefly to the 

 demersal group, especially in Syngnathus, and in the following year 

 Hubbard described it carefully in the eggs of a viviparous American fish 

 f Gymatogaster ), in which he found that it continued until the closure of 

 the blastopore.§ More recently Cunningham has given an account of 

 its presence in teleostean eggs.H The true function of the vitelline 

 nucleus has been much discussed. Two things are significant in connec- 

 tion with its appearance in the cytoplasm. One is the fact that it 

 precedes the formation of yolk-granules in the peripheral zone to which 

 it moves. The other is the fact that it is more commonly to be observed 

 in demersal eggs, in which the yolk is more concentrated, than in pelagic 

 eggs, and that then more than one may exist. 



Some observations which I have recently made, most fully on the 

 eggs of the angler and John Dory, are of some interest in connection with 

 the elimination of chromatic substance from the germinal vesicle. They 

 may be given here, although I have been unable, for want of time, to make 

 drawings illustrating all the points described, which I hope to do later. 



In LopMus^ as elsewhere described (page 125), the minute ova 

 are to be found at the base of the ovigerous pouches. In sections of the 

 ovary of a specimen caught on 5th March, hardened in platino-aceto- 

 osmic mixture and stained with hsematoxylin, saffranin, and eosin, and in 

 which the largest eggs in a pouch measure about 0'109mm., the most 

 minute eggs at the base measure about 0-0056mm. They are not much 

 larger than the rounded cells seen in the epithelial layer, which measure 

 from 0 0035 to 0 •0042mm., and they present precisely the same appear- 

 ance when examined with Zeiss' 2mm. oil-immersion and compensating 

 ocular 6 ; that is to say, they are clear vesicles, with a minute but con- 

 spicuous, brilliantly stained (red) spherical nucleolus placed in the centre, 

 or somewhat excentrically, a scanty network that cannot be well seen, and 

 no protoplasm around. In those a little larger, measuring about O'OOTmm., 

 the nucleolus measured 0'0018mm., and the network could be more dis- 

 tinctly traced in the form of a few, relatively thick, granular threads 

 radiating from the nucleolus and showing at points slight thickenings of 

 the nature of karyosomes. The threads are very few compared with later 

 stages, and they are also thicker; from three or four to about a dozen 

 may be seen passing from the nucleolus, sometimes in a radial manner, 

 like the spoke of a wheel ; and on focussing the periphery the thicken- 

 ings appear as dots radially disposed around it. There is still no 

 cytoplasm. 



In eggs a little larger, measuring about 0'0098ram., the network is 

 seen to have considerably increased, but the meshes are still wide ; the 

 prominent nucleolus has disappeared, and in its place numerous more 

 minute, red-stain(5d karyosomes are to be observed at intervals throughout 

 the network; the condition suggests that the nucleolus has melted or 

 become diffused. In eggs a little larger, from about O'Ollmm., a very 



* Elimination d'elements nucleaires dans I'oeuf ovarien de Scorpcma sorofa.-^Aroh. de 

 Biol, xiii., p. 88. 1893. 

 t Bull. Acad, des Roy. Set. Brxixelles, 3 Ser., Tom. vi., p. 843. 1888. 

 X Jour, de I'Anat. et de la Physiol., N.S., Vol. xxix., p. 1. 1883. 

 § Proc. Amer. Phil. Sac, xxxiii., p. 74. 1894. 

 II Op. cit. 



