412 F. M. BALFOUR. 



is only one in eacii 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 tilled with 

 numerous deeply staining s])herical 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 

 (6g, 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 show the size of some of these 

 bodies in relation to the germinal vesicle and ovum: — 



Diameter of Germiual Diameter of Body in 



Diameter of Ovum. Vesicle. Vitellus. 



096 mm. . . 0-03 mm. . , 0-009 mm. 

 064 mm. . . 0-0:i5 mm. . . 0012 mm. 



0096 mm. . . 03 mm. 



[t 



019 mm. 

 003 mm. 



Germinal vesicle. — Gegenbaur^ 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^ states that there is nothing remarkable in 

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

 reaches 0'5 mm., a single germinal spot is always present (mea- 

 suring about 01 mm.), which is absent in larger ova. 



The bodies described by Gegenbaur are now generally recog- 

 nised as germinal spots and will be described as such in the 

 sequel. I have very rarely met with the condition with the 

 single nucleolus described by Schultz in Torpedo. 



My own observations are confined to Scyllium. In very young 

 females, with ova not larger than 0*09 mm., the germinal vesicle 

 has the same characters as during the embryonic periods. The 

 contents are clear but traversed by a very distinct and deeply 

 staining reticulum of fibres connected with the several nucleoli 

 which are usually present and situated close to the membrane. 



In a somewhat older female in the largest ova of about 

 0"12 mm., the germinal vesicle measures about 00 mm., and 

 usually occupies an excentric position. It is provided with a 

 distinct though delicate membrane. The network, so conspicuous 

 during the embryonic period, is not so clear as it was, ami 

 has the aj)pcarance of being formed of lines of granules rather 



' Loc. cit. 

 ' Loc. cit. 



