INTRA-OVARIAN EGG OF SOME OSSEOUS FISHES. 59 



outlines of its predecessor, we are at once struck by the peculiar 

 protuberances which make their appearance all over its outer 

 surface. They were best seen in sections through the hardened 

 ova of the gurnard. These measured somewhere about O130 

 mm. in diameter. These diverticula, buds or " stolons," as 

 they have been called by Balbiani, are pushed out by the 

 nucleus. Part of the nucleoli resting upon the diverticula is 

 drawn into them and carried away towards the exterior of the 

 egg. They have the appearance now of minute vesicles or 

 cells containing a nucleus. For such, indeed, they have been 

 mistaken even by the most recent writer on the subject, Ovsi- 

 annikov. The vesicle is either a portion of the nuclear wall 

 which has become constricted off, or it may be a later forma- 

 tion. Sometimes the vesicles thus formed do not contain any 

 nucleolar matter and remain unaffected by staining reagents. 

 Like the others they travel towards, but they do not quite reach 

 the surface of the egg, leaving a cortical layer of protoplasm 

 which is the " Rindenschicht " of His. The vesicles with their 

 nucleolar contents are the yolk-spherules. The solid mass 

 in their interior soon breaks up into fine granules, and it is in 

 this condition that the yolk-spherules are found in the largest 

 intra- ovarian eggs. The granules, however, are at first of a 

 dark colour, which they only lose on the ovum becoming ripe. 

 In the mature egg the yolk is perfectly transparent. 



The nuclear network which has been mentioned above is 

 specially well seen at this stage (Fig. 9, n.f.). The threads 

 connecting the minute granules in the interior of the nucleus 

 seem to be made up of fine dots rather than solid fibres. 



The vesicles with clear contents might possibly be what is 

 known as " oil globules/' on the significance of which my friend 

 Mr. Prince 1 has recently published an interesting paper. Their 

 oily contents would thus originate from the clear nuclear sub- 

 stance. I merely throw this out as a suggestion, but if it should 

 ultimately be proved correct, it would form another addition to 

 these most interesting and instructive phenomena which the 



1 Prince, Ed. E., "On the Presence of Oleaginous Spheres in the Yolk of 

 Teleostean Ova," ' Ann. Nat. Hist.,' 1886. 



