284 LOUISE HOYT GREGORY. 



In commencing the work, the material at first showed the 

 nephridia to be so small that it seemed impossible that the large 

 eggs could pass out through them. Goodrich's supposition that 

 the eggs might pass to the outside through a break in the body 

 seemed at first to be confirmed in some of my sections. I found 

 cases where there appeared to be a definite rupture in the center 

 of the ventral longitudinal muscles. This interpretation, how- 

 ever, was proved false, first by the fact that the eggs passing 

 through the rupture were immature, ovarian eggs, whereas, in 

 general, the eggs have been found to form their first polar spindle 

 before leaving the body, and second, by the discovery of eggs pass- 

 ing along the ciliated organ and down into the nephridial cavity 

 (Figs. 3 and 4). The walls of the nephridium are thin, but elas- 

 tic and are capable of great expansion at the time of maturity. 

 The inner end of the tube swells as the eggs become matured. 



NP 



Fig. 4. X 5°°- A sagittal section of the nephridial sac showing the external open- 

 ing at the lower end. N, nephridial sac; N.P, nuclear plate showing that the 

 first maturation spindles are formed before the eggs are extruded. All of the eggs 

 are in the same stage of development, the nuclear plates being visible in different sec- 

 tions. 



(The beginning of this is shown in the nephridium in Fig. 1.) 

 Finally the whole tube is distended and has the appearance of a 

 large irregular sac filled with sexual products (Fig. 4). The 

 eggs may pass into the nephridium before forming the polar spin- 

 dles which are formed in that case, while the eggs are in the ne- 

 phridial sac. This was probably the case in Fig. 4, or as has been 



