ELISHA MITCHELL SCIENTIFIC SOCIETY. IO3 



size of the cells, cannot be followed with the same accu- 

 racy as in Esperella, but the process can be seen to be 

 essentially the same. The "segmentation," or gradual" 

 dissolution of the gemmule into its constituent cells, takes 

 place in the same w^ay. The swimming larva is, except 

 in a few details, like the larva of Esperella, and the 

 metamorphosis takes place on the same lines. 



In the tgg development of Tedanione, there is a total 

 segmentation, resulting in the formation of a solid morula. 

 The larva, when set free, is a solid oval body, completely 

 covered with a layer of columnar ciliated cells. The 

 metamorphosis was not observed. The segmentation of 

 Hircinia is likewise a total segmentation, resulting in the 

 formation of a solid morula. The development of the 

 ovarian tgg in these two forms is essentially alike. The 

 follicle during the growth of the ^gg is surrounded by a 

 large number of comparatively densely packed mesen- 

 chyme cells, the duty of which is presumably to bring 

 nourishment to the growing -egg (compare Fiedler's account 

 for Spongilla). The nucleus of the very young &gg con- 

 tains a single large nucleolus more or less centrally placed. 

 While the egg is comparatively small, before it has reached 

 more than one-half its ultimate size, two small spherical 

 masses of densely staining chromatin are found adhering 

 to opposite sides of the inner face of the nuclear w^all. As 

 a rule, in eggs which have reached the full size, only one 

 or neither of these chromatine balls is present. 



Occasionally, however, an egg is found of the full size 

 and still with both of the chromatin balls. One of the 

 masses is probably lost (thrown out ?) about the time when 

 the increase in size is completed. The remaining mass is 

 thrown out of the nucleus, and may sometimes be observed 

 lying in the egg yoke near the nucleus. The nucleus of 

 the ripe egg thus left without chromatin mass, is a poorly 

 defined bodv in which neither nuclear membrane nor 



