278 LILIAN SHELDON. 



the rest of the germinal epithelium, the limit being marked 

 only by the density of the former. 



By September (v. fig. 4) the ovum has increased considerably 

 in size, has acquired a definite oval shape, and is enclosed in a 

 very thin shell. The nucleus is round, has a central position, 

 and encloses a round excentric nucleolus. The peduncle con- 

 necting the ovum with the ovarian wall has become larger and 

 is still many cells thick. 



An ovum of this date (September), with its stalk, is shown 

 in fig. 5 : the nucleus contains a protoplasmic reticulum with 

 special aggregation of chromatin at the junctions of the strands, 

 and also a round, excentric nucleolus. 



From this time onwards the ova gradually increase in size, 

 and the peduncles grow longer and thinner. The nucleus and 

 nucleolus also become larger and the shell acquires considerable 

 thickness. 



In the youngest ovum (v. fig. 8) which I have found in the 

 ovary of April, the nucleus still has a central position and 

 contains a large round nucleus, which is slightly excentric, 

 stains very deeply, and encloses some highly refractive chro- 

 matin and some very small vacuoles. The nucleus is granular, 

 and not very difinitely marked ofi" from the cell-protoplasm ; 

 but I am not able to trace any distinct connection between 

 the reticula of the two. The shell is very thick. The cell- 

 protoplasm has a granular structure, and contains numerous 

 very minute, highly refractive globules, which appears to be 

 yolk. The stalk is long, and is, through most of its length, 

 two cells thick. 



The next event is the travelling of the nucleus from the 

 centre to the periphery of the ovum, at the side removed from 

 the point of attachment of the stalk. The protoplasm also 

 loses its dense character and becomes looser. The nucleus has 

 a definite wall, which is continuous with the meshwork of the 

 protoplasm. 



In the next stage (v. fig. 9) the protoplasm is still less dense 

 and more loosely reticulate ; the nucleus lies quite periphe- 

 rally, is homogeneous in structure, and has lost its nucleolus. 



