124 CHAS. B. WILSON. 



thelial cells into tlie underlying connective tissue. As the 

 ovum matures the neck of the flask is gradually pinched off 

 from its connection with the epithelium^ and the egg is set 

 free in the central cavity (ec.'"). 



It is not, however, naked as at first, but is now invested 

 with a delicate follicle, and is soon surrounded by a thick 

 layer of gelatine, both of which are apparently formed from 

 adjacent epithelium cells. As fast as an ovum is pinched off 

 into the central cavity the epithelium partly closes behind it 

 and new ova are formed, this process continuing until the 

 whole pouch is filled. 



Interspersed among the ova and scattered through the jelly 

 which fills the central cavity are small spherical highly pig- 

 mented bodies, granular in structure. 



These are probably the same as those described by 

 Hubrecht (27) for Drepanophorus and Cerebratulus 

 raarginatus, and like them they disappear gradually as the 

 ova ripen. Hence they must contribute to the development 

 of the egg, and undoubtedly furnish the yolk material. 

 There are also other cells, slightly smaller and lighter in 

 colour, but staining more deeply, which are scattered all 

 through the central cavity. From these comes the gelatine 

 which fills all the space not occupied by eggs (gc, fig. 65). 



In a ripe ovary the eggs are crowded together so closely 

 that they become more or less angular in outline. 



If a mass of these eggs be examined before they have 

 touched any water they present the appearance seen in 

 fig. 18. Each egg is separated from its fellows by the thick 

 layer of transparent gelatine which surrounds it. This is 

 bordered in turn by a stiffened external surface, where it 

 comes in contact with the coats of adjacent eggs. This gives 

 the whole mass somewhat the appearance of honeycomb, 

 made up of angular gelatinous cells, with an egg in each cell 

 very near its centre. 



The gelatinous envelopes cling to the eggs almost as firmly 

 as the similar jelly around amphibian eggs (Amblystoma, 

 etc.), and they evidently serve the same purpose. 



