11 



of spayming. The specimen was held inverted in a v/atch- 

 glass under the microscope, Althoixgh not Tree to swim, it 

 went throush the motions, contracting the bell rythmically. 

 In this way the softened ectodermal tissue of the gonad was 

 ruptured, and the e^gs expelled. Little round pits are 

 left by the ep;gs , like bullet-molds. The earliest date at 

 which fertile medusae have been found was the first of Ju- 

 ly; the latest, the last week of September, The period of 

 maximum sexual activity is from the middle of July to the 

 middle of August, 



B. Periodicity - As stated by Murbach (1895) the 

 eggs are normally extruded at about eight o'clock P.M. This 

 is the case during the earlier part of the summer, but lat- 

 er in the season, when the days are shorter, half-past sev- 

 en, or even shortly after six is the normal time for spawn- 

 ing. Further than this, extrusion of the eggs may be arti- 

 ficially induced in Gonionema, In this respect this form 

 differs markedly from some other marine animals which ex- 

 hibit equally definite times of spawning. Dr. Ilurbach 

 found that during the daytime after being shut up for an 

 hour in a dark place the ripe medusae would deposit eggs 

 and sperm. My experiments show that this is true in the 



