AKTIFICIAL PARTHENOGENESIS IN ANNELIDS 669 



157) was made. It is impossible to recognize any distinct 

 cleavage spheres in these eggs. All that can be said is that 

 they have lost their spherical outline and are amoeboid. I 

 have never seen anything like this in fertilized eggs, or in 

 the unfertilized control eggs that are left in normal sea-water. 

 If the latter segment at all, they do not begin to do so until 

 after seven to nine hours or later, and they form more dis- 

 tinct cleavage cells. 



The appearance of the eggs and the form of segmenta- 

 tion are thus distinctly a function of the constitution of the 

 sea-water. Inasmuch as the K eggs give rise to trocho- 

 phores which may look as normal as those developing from a 

 fertilized egg, it is evident that the appearance of the cleav- 

 age cells is of very little importance in the formation of the 

 embryo. 



The difference between the development of unfertilized 

 K eggs and fertilized eggs can be seen from Fig. 158. In 

 the experiments in which these drawings were made the eggs 

 of one female were divided into two lots. The one was 

 fertilized at 11:45 by the addition of sperm; the other was 

 put at the same time for fifty-five minutes into a mixture of 

 98 c.c. sea-water -f- 2 c.c. 2^n KC1. In about fifteen to 

 twenty minutes after the eggs were put into this mixture 

 they threw out their polar bodies; sometimes one, sometimes 

 two were visible. This harmonizes with Mead's observations. 

 In the unfertilized control eggs that had remained in normal 

 sea-water nothing of this kind was noted. 



Fifty-five minutes after the eggs had been put into the 

 KC1 mixture they were put back into normal (sterilized) sea- 

 water. In from ten to thirty minutes they began to lose their 

 spherical shape, and in some eggs little processes or knobs 

 appeared and remained or were withdrawn. The eggs 

 resembled amoebae in their behavior. In Fig. 158, on the 

 left side, the development of the fertilized lot is represented; 



