EGG-LAYING HABITS OF AMHIITRITE ORNATA VERRILL. 339 



2. The moon does not have any direct influence in producing 

 the period of sexual activity. It is probable that the tide also 

 has little, if any, direct effect on the process. 



3. At spring tide, the worms feed more actively, the food sup- 

 ply is more abundant and the sand flats have a higher tempera- 

 ture. As this period approaches we also find a more rapid growth 

 and development of immature eggs and sperm. Therefore, the 

 period of sexual activity is closely associated with a synchronous 

 period of greater bodily activity, and this greater vigor of the 

 animal is induced by conditions that depend upon the tide. In 

 this way we may explain how oviposition in Amphritite has be- 

 come a sort of reflex habit associated with the time of spring tide. 



4. When a worm is sexually mature, the ccelomic fluid contains 

 ccelomic corpuscles and eggs in various stages of development. 

 At oviposition the worm extrudes ripe eggs, and toward the end 

 of the process some of the immature ones, but always retains the 

 much smaller ccelomic corpuscles. 



5. Since the mature eggs sink faster in sea- water than the 

 smaller immature ones, and all eggs sink faster than the ccelomic 

 corpuscles, it is believed that the larger eggs have a greater 

 density than the other bodies in the ccelomic fluid ; and it is en- 

 tirely probable that the apparent selection of ripe eggs and the 

 rejection of immature ones is due to the different effects pro- 

 duced by nephridial currents upon bodies of apparently different 

 densities. 



6. The position of the nephridial sacs, and the arrangement of 

 cilia on the nephrostomes and within the sacs, is such that we may 

 regard the nephridia as a set of settling basins in which the sepa- 

 ration takes place. Contractions of the worm's body then aid in 

 expelling the ripe eggs from the nephridial sacs. 



BIBLIOGRAPHY. 



Gamble and Keeble 



'06 The Bionomics of Convoluta roscoffensis, with Special Reference to its Green 



Cells. Quar. Jour. Microscopical Sci., XLVII., p. 401. 

 Gerould, John H. 



'06 The Development of Phascolosoma. Zool. Jahrbucher, Bd. 23. 

 Leidy, Joseph 



'55 Marine Invertebrate Fauna of the Coasts of Rhode Island and New Jersey. 

 Jour. Acad. Nat. Science, Philadelphia, II., Vol. III. 



