582 THE STRUCTURE AND DEVELOPMENT 



of the yolk, and the fact of their not staining with osmic acid 

 is strongly opposed to this view of their function. Dr Eimer 

 does not appear to me to bring forward any satisfactory proof 

 that they are in any way related to the formation of the yolk, 

 but wishes to connect them with the peculiar body, well known 

 as the yolk nucleus, which is found in the Amphibian ovum 1 . 



Another peculiar body found in the ova may be mentioned 

 here, though it more probably belongs to the germinal vesicle 

 than to the yolk. It has only been met with in the vitellus 

 of some of the medium sized ova of a young female. Examples 

 of this body are represented on PL 25, fig. 25 A, x. As a rule 

 there is only one in each of the ova in which they are present, 

 but there may be as many as four. They consist of small vesicles 

 with a very thick doubly contoured membrane, which are filled 

 with numerous deeply staining spherical granules. At times 

 they contain a vacuole. Some of the larger of them are not 

 very much smaller than the germinal vesicle of their ovum, 

 while the smallest of them present a striking resemblance to 

 the nucleoli (fig. 25 'B), which makes me think that they may 

 possibly be nucleoli which have made their way out of the 

 germinal vesicle. I have not found them in the late stages or 

 large ova. 



The following measurements shew the size of some of these 

 bodies in relation to the germinal vesicle and ovum : 



Diameter of Germinal Diameter of Body in 



Diameter of Ovum. Vesicle. Vitellus. 



0-096 mm. . . O'O3 mm. . . o'oog mm. 

 0*064 mm ' 0-025 mm - 0*012 mm. 



fo-oio mm. 

 o'oo6 mm. . . 0*03 mm. . . \ 



(p'oo3 mm. 



Germinal vesicle. Gegenbaur 2 finds the germinal vesicle 

 completely homogeneous and without the trace of a germinal 

 spot. In Raja granules or vesicles may appear as artificial pro- 

 ducts, and in Acanthias even in the fresh condition isolated 

 vesicles or masses of such may be present. To these structures 

 he attributes no importance. 



Alexander Schultz 3 states that there is nothing remarkable 

 in the germinal vesicle of the Torpedo egg, but that till the egg 



1 Vide Allen Thomson, article "Ovum," Todd's Encyclopedia, p. 95. 

 ' 2 Loc. cit. 3 Loc. cit. 



