OVARY AND OVARIAN OVA IN CERTAIN MARINE FISHES. 131 



gat us, Gibbons, one of the viviparous Embiotocidse of the 

 Pacific coast. The eggs of this fish are very smallj and develop 

 scarcely any yolk. The earliest stage of the vitelline corpuscle 

 which Hubbard could discover was, like that which I have 

 described, a crescent-shaped body, fitting closely to one side 

 of the nucleus. The eggs in which this condition was observed 

 were 20 fx, or '02 mm., in diameter. In later stages the body 

 was found at a distance from the germinal vesicle. It tra- 

 velled towards the periphery of the ovum, and remained visible 

 even in the period of segmentation. Hubbard concludes that 

 the body originates from the nucleus. 



The later history of the vitelline nucleus in Pleuronectidse 

 is as follows : — It moves away from the germinal vesicle to- 

 wards the periphery of the ovum, as seen in fig. 21. When 

 the deposition of yolk commences in the peripheral layer of 

 cytoplasm, the vitelline nucleus is seen close to the inner limit 

 of the yolk, and the body then assumes somewhat the form of 

 a sphere at the apex of a cone. The conical portion is in con- 

 tact with the yolk layer at its base, and careful examination 

 shows that it is continuous with the strands of cytoplasm 

 which separate the yolk globules. This condition is shown in 

 figs. 10 and 14. Usually the cone can be seen to give off 

 divergent strands which pass into the cytoplasmic network, 

 and then the vitelline body reminds one forcibly of the form 

 of an octopus, with its arms extending into the yolk. In the 

 spherical portion of the body vacuoles appear, and these ap- 

 pear to be similar to those which contain the yolk globules, 

 but I am not certain whether they actually contain yolk sub- 

 stance or not. As the yolk layer increases in thickness, the 

 vitelline body becomes completely surrounded by it, and is 

 then detected with some difficulty as a little island of cyto- 

 plasm rather more deeply stained than the rest, and compara- 

 tively free from yolk. After the yolk has reached the surface 

 of the germinal vesicle, I have not been able to detect the 

 vitelline nucleus. 



The structure in question is very much less conspicuous in 

 the ova of the grey gurnard in my preparations than in those 



