IO6 H. H. NEWMAN. 



of direct sunlight. For purposes of observation eggs were re- 

 moved from time to time and placed in watch-glasses with a ster- 

 ilized pipette. It was thought safer not to run, as direct controls, 

 normally fertilized eggs, but on other days and under identical 

 conditions numerous observations were made on the course of 

 normal fertilization and development. The differences observed 

 between the behavior of parthenogenetic and that of fertilized 

 eggs were so striking that it seemed well worth while to study 

 and to describe them. 



PECULIARITIES OF THE MATERIAL USED. 



Asterina (Patiria) miniata is one of the commonest starfishes 

 of the California coast. It is a relatively small species in which 

 the five rays are almost completely amalgamated with the central 

 disc in such a way as to give the creature a nearly pentagonal out- 

 line. In color it ranges from a brilliant scarlet to a light cream 

 color with various intergrades and piebald combinations. It 

 seems likely that there are several subspecies that freely inter- 

 breed. My experience seems to indicate that relatively few eggs 

 mature at a time and are exuded in small numbers over a long 

 season. Among the very large number of females examined I 

 never found an ovary that showed any large percentage of ripe 

 eggs. Those that were shed from the removed ovary and gently 

 shaken in sea water contained oocytes in all stages of develop- 

 ment, some quite small, others fully grown but incapable of mat- 

 uration, still others mature and ready for maturation and fer- 

 tilization after standing about one and a half to two hours in sea 

 water. None of the eggs when freshly shed had undergone matu- 

 ration. This may mean that the artificial shedding of the eggs 

 is a premature process, and that, as seems to be the case in some 

 asteroids, if the eggs were to be normally extruded through the 

 genital pores, they would be immediately ready for fertilization. 

 I have never been able to observe the extrusion of eggs in As- 

 terina, nor to induce it by massaging, as can be done in some 

 asteroids. This may possibly be due to some peculiar sexual 

 rhythm in this species, which results in ovulation occurring only 

 at night or at some particular phase of the moon or of the tide. 



