EGG-LAYING IN AMPHITRITE. 



253 



interesting question then arises, How are ripe eggs separated from 

 the other ccelomic bodies in the act of oviposition? 



REFERENCES TO PREVIOUS PAPER. 



At first an attempt was made to answer this question by 

 studying the general anatomy of Amphitrite. In this group, as 

 shown by Meyer, the septa are incomplete or absent, with one 

 exception. The one complete septum, called the diaphragm, is 

 near the anterior end and divides the ccelome into two unequal 

 cavities. Anterior to the diaphragm the nephridia are for ex- 



t o fl 



FIG. i. To show the comparative size and shape of various bodies found in 

 the coelome of Amphitrite at the time of egg-laying; a, red blood corpuscles; b, 

 youngest free egg observed; c, young egg, with little or no yolk; d, unripe egg, nearly 

 mature; e, mature egg. Both edge and side views shown. 



cretion only. The posterior nephridia are modified as gonaducts, 

 and it is with these last that we are concerned. Their inner 

 openings are bordered by large folded, or fimbriated, membranes, 

 covered by strong cilia. Each opening connects with a large 

 vascular sac, also ciliated. From these sacs tubes pass to the 

 outer openings of the nephridia which are found in the species 

 studied on segments 6-10 inclusive. From the dissections I 

 came to the conclusion that there was no apparatus for sifting 

 or "straining out" the ripe eggs. 



