SECT. X REPRODUCTION 143 



is apparent that the vanishing of these nephridial 

 tubes could be nothing but pure gain ; the simpler 

 and the less differentiated the duct which they have 

 to stretch in passing out, the better. 



The eggs appear to develop out of indifferent 

 epithelial cells at the dorsal and ventral tips of the 

 genital glands. Their very first stages we have, how- 

 ever, not been able to trace. They are first recognis- 

 able as small groups of four cells with large nuclei 

 (see Fig. 33), embedded among the undifferentiated 

 epithelial cells. The nuclei show characteristic 

 differences from the first stage at which we have found 

 them. One is clear and round, with one or at the 

 most two germinal spots ; the other three are slightly 

 larger and quite full of irregular deeply stained 

 granules. The former is the nucleus of the future 

 egg, the latter are the nuclei of the nutritive 

 cells. 



The four cells grow together in one compact mass 

 to a great size, the partitioning membranes being, 

 however, traceable. They bulge out the membrane of 

 the genital tube into the body cavity. In successful 

 preparations, fine nuclei of a tesselated follicular 

 epithelium can be found between the eggs and this 

 membrane (Fig. 33,;/). When the egg has been dis- 

 charged down the branch into the genital tube, the 

 locus of the egg is found as a small shrunken bag full 

 of minute round bodies which are doubtless these 

 follicle cells thrown off by the shrinking of the mem- 

 brane (Fig. 33,6). This epithelium then apparently 

 plays no very important part, unless, in some way, it 



