THE DEVELOPMENT OF THE MOLE. 207 



to decide, but the appearance of the nucleoli in figs. 4 and 5, 

 considered in connection with the researches of Griiber (No. 

 12) on the nuclei of Protozoa, would suggest that such is 

 the case. 



Mature Ovarian Ovum. 



The phenomena of the maturation of the ovum I have not 

 had an opportunity of observing in all its phases, but I have 

 been fortunate enough to obtain a fully mature ovarian ovum 

 (or one almost in a mature condition) which has been repre- 

 sented in fig. 8. 



In this latter the ovum lies freely within the zona radiata 

 and is separated from it by a considerable space, the circum- 

 vitelline space in which, according to v. Beneden, is a 

 fluid, the circum-vitelline fluid. The vitelline membrane 

 is here distinctly seen on account of the contraction, of the 

 substance of the vitellus. 



The ovum itself is very dense and contains a number of dark 

 granules not observed in less mature ova ; it is separated from 

 the vitelline membrane by a narrow space excepting (1) at 

 certain points where pseudopodia-like processes of the vitellus 

 project across the space and are attached to the vitelline mem- 

 brane, and (2) at one spot where no contraction of the ovum 

 has occurred. At this latter point the vitellus is more trans- 

 parent than elsewhere, and the nucleus may there be seen in 

 close approximation to a dark oval body lying immediately 

 outside the vitelline membrane, while a second more trans- 

 parent oval body in which is a central dark mass may be seen 

 lying in the midst of the circum-vitelline space. These two 

 bodies are the polar bodies {p. b.),the second of which has but 

 just been produced ; while the nucleus seen within the ovum 

 is the female pronucleus (/. p.). 



It is possible to describe the vitellus as composed of a 

 cortical more clear, and a medullary granular portion such as 

 Beneden (No. 5) describes in the mature ovarian ovum of the 

 Rabbit, but the boundary of these layers is by no means easy 

 to define. The light-coloured space in which the nucleus is 



