DEVELOPMENT OF PARA VORTEX GEMELLIPARA 485 



of capsules containing three or four embryos than is met with 

 in the latter species. 



a. The process in Paravortex gemellipara. The general plan 

 and appearance of the ovaries, vitellaria and antrum of P. 

 gemellipara supports the hypothesis that a similar process occurs 

 here. As described in the introduction, the antrum femininum 

 bifurcates at its distal end, sending a thin-walled branch, the 

 oviduct, to meet the ends of the ovaries and vitellaria of each 

 side. 



Examination of the posterior end of either ovary in animals 

 which have reached the egg-producing stg,ge usually shows that 

 the last, and hence the ripest, egg is being pressed inward to- 

 ward the antrum by the ova behind it. Posteriorly the com- 

 pact vitelline cells crowd the egg in a forward direction so that 

 it appears, in a frontal section, as in figure 4. Here the ter- 

 minal egg of each ovary is being subjected to the same conditions. 

 The one on the right seems just in the act of being forced into 

 the oviduct. Such is the usual picture, an egg from each ovary 

 on the verge of entering the oviduct. Only a slightly greater 

 pressure is required to complete the process. Suppose the 

 worm were now to contract its body in this general region; the 

 probable result would be that both ova would enter the antrum. 

 Most conclusive visual evidence is to be gained from a series 

 of sections of a specimen which had been killed in the most criti- 

 cal stage, where two eggs had just been set free and were being 

 surrounded with the yolk cells from the vitellaria. The sections 

 are slightly oblique between a vertical longitudinal and a frontal 

 plane, somewhat nearer the latter. 



Figure 9 drawn from the " specimen under consideration, 

 shows what is taking place. Apparently the right ovary, part 

 of which is included in the section, was distorted and crowded 

 inward by the contraction of the animal in the fixing fluid. 

 Otherwise it would have been impossible to have cut a section, 

 which would include, as this does, seminal vesicle, antrum and 

 ovary. Aside from the retention of a deeper stain these two 

 ova are in the same condition as the eggs at the end of the ovary. 

 The nuclei of both are resting, and their chromatin and nucleoli 



