1886.] OVUM OF LEPIDOSIREN. 277 



membrane of the germinal vesicle is not always very obvious ; 

 but as there is a sharp contrast between the protoplasm of the 

 germinal vesicle and the surrounding substance of the ovum (indi- 

 cated by the much deeper staining of the former by borax carmine), 

 there comes to be an appearance of a delicate memhrane surrounding 

 the germinal vesicle ; this membrane has not a double contour. 



In younger ova there is a very distinct membrane bounding the 

 germinal vesicle externally ; this membrane is more easily to be 

 distinguished in my preparations from the fact that it is very deeply 

 stained. 



Although the boundaries of the germinal vesicle are distinct 

 enough, there is no cavitv dividing it from the egg-protoplasm ; the 

 granules of the latter are everywhere in contact with the germinal 

 vesicle. In several preparations the germinal vesicle had shrunk ; 

 but in every case observed by me the wall of the germinal vesicle 

 was covered with egg-protoplasm granules, thus showing that the 

 spaces surrounding the germinal vesicle in that figure are not 

 natural, but due to alterations caused by the contraction of the ger- 

 minal vesicle. 



The interior of the germinal vesicle is occupied by a finely- 

 granular matter, which is almost homogeneous throughout. In 

 certain tracts, however, the granules are more deeply stained and 

 often larger; these granules form a reticulum (Plate XXIX. fig. 3). 

 In the ovum of Triton, Iwakawa illustrates {loc. cit. pi. xxiv. fig. 27) 

 a very similar condition of the nucleoplasm. The germinal spots 

 are very numerous, and form a layer surrounding the germinal 

 vesicle ; the latter is shown on a superficial view in fig. 3, and in 

 transverse section in Plate XXIX. fig. 4. The germinal spots are 

 of very varying size, and usually oval or circular in form ; borax 

 carmine stains them more deeply than the surrounding nucleojjlasm ; 

 they are evidently not homogeneous, but appear to consist of au 

 outer sheath of stout consistency, and very deeply stained by the 

 reagent, and within this an apparently more fluid core which is not 

 deeply stained. 



The presence of numerous germinal spots is figured by Ayers 

 for both Ceratodus (plate xviii. fig. 76) and Lepidosiren (plate xvii. 

 fig- 27). 



It is also characteristic of the Teleostean ovum , and is mentioned 

 by Messrs. Balfour and Parker - in Lepidosteus. Among Amphibia 

 Triton shows the same condition of the germinal spots. In ova of 

 the stage represented in Plate XXVIII. fig. 2, the substance of the 

 ovum which immediately surrounds the germinal vesicle differs from 

 the rest in being more loosely compacted. 



In ova which are distinguished by the enormously increased 

 functional activity of the follicular epithelium, the germinal vesicle 

 could not be found. In all probabihty, however, my failure to find 

 the germinal vesicle is not due to its absence. 



^ Brock, " Beitrage z. Anatomie und Hiatologie der Geschlechtsorgane der 

 Knochenfische," Morphol. Jahrb. Bd. iv. (1878) p. 505, pi. xxviii. figs. 8, 11. 

 ^ " On the Anatomy and Developmeut of Lepidosteus," Phil. Trans. 1884. 



