112 H. H. NEWMAN. 



commonly adopted'by experimentors upon like material. As an 

 introduction to the experimental part of this paper we shall ask 

 the reader to make with us a brief survey of the essential features 

 of the normal embryonic and larval periods of Patiria, paying chief 

 attention to the origin and development of asymmetry. 



II. THE NORMAL DEVELOPMENT OF Patiria. 



Methods of Securing and Handling Eggs and Larva. Patiria, 

 miniata is a common Pacific Coast starfish with which I have done 

 considerable work. During the spring of 1920 I had not dis- 

 covered any better method of securing the eggs than that of 

 shaking the excised ovaries in bowls of sea-water. This method 

 had proven rather unsatisfactory because the great majority of 

 eggs thus obtained were immature and incapable of fertilization 

 even after standing for an hour or so. Furthermore, the presence 

 of so many dying and disintegrating eggs tends to foul the water 

 and to encourage the development of deleterious bacterial and 

 fungoid growths, which are far from favorable for the living and 

 active larvae. This difficulty was formerly obviated to some 

 extent by taking advantage of the fact that there is a certain 

 period in the early larval life when all healthy larvae swim to the 

 surface and thus may be decanted off and placed in clean sea 

 water. But many of the slightly subnormal larvae fail to reach 

 the surface and either have to be picked out individually or left 

 to develop amidst the debris of decaying eggs. 



The improved method takes advantage of the chance obser- 

 vation that if ripe starfishes are allowed to stand for a few hours 

 out of water they shed both eggs and milt in great volume. The 

 procedure adopted was to place a considerable number of freshly 

 collected starfishes upon a bed of seaweeds in a moist atmosphere. 

 It is found that about ten per cent, of the individuals shed their 

 genital products within from two to four hours and that both eggs 

 and sperms are uniformly ripe and in prime condition, so that 

 essentially all eggs are fertilized and develop normally. Many 

 thousands of eggs may be shed within a few minutes by a single 

 female, making it possible to conduct several experiments with a 

 single batch of eggs. Variety may be secured by fertilizing one 

 lot of eggs with the sperm of several males. It is necessary to use 



