42 HARRIETT M. ALLYN . 



ment of substances in the cells is in general normal. A good 

 many larvae are abnormally segmented, often one cell having 

 stopped in an early stage of cleavage, and the others having gone 

 on and divided further. The larvae fixed at 21 hours (Fig. u) 

 are mostly abnormal, apparently, but one or two were found in 

 the living material which showed even the long apical flagellum. 

 On the whole the series approaches much more nearly to the 

 normal development than any other series I have so far been 

 able to obtain, chiefly because here, and nowhere else, could I get 

 mitotic cleavage to any extent. The possibility of the develop- 

 ment of unfertilized eggs to swimming larvas having been estab- 

 lished, the question of inducing a cleavage process to accompany 

 this development was the next important step. Cleavage ob- 

 tained, it will now be necessary to vary conditions in such manner 

 that the abnormalities arising in the cleavage with the present 

 method may be avoided. The later development of the larvas, 

 beyond the trochophore stage, I have not attempted, as my 

 first interest lay in the initiation of normal development. 



IV. COMBINATION OF TWO AGENTS. 



In order to form a check on the effect of the various agents 

 upon the unfertilized eggs, artificial parthenogenesis was supple- 

 mented by fertilization in a number of cases, sperm being added 

 after the eggs had been treated by a physico-chemical agent. In 

 other cases the effect of supplementing the action of one physico- 

 chemical agent by that of another was tried, and in many 

 instances the results of treatment with two physico-chemical 

 agents were similar to those produced by using one such agent 

 and fertilization. 



A. Artificial Parthenogenesis, Supplemented by Fertilization. 

 Eggs were fertilized after application of an artificially stimulating 

 agent. The parthenogenetic agents used as a preliminary to 

 fertilization were KC1, low temperature, and oxygen-saturated 

 sea-water. In general it may be said that the agents, of whatever 

 sort, which will induce development in unfertilized eggs, are 

 prejudicial to normal development in fertilized eggs. 



i. Potassium Chloride and Sperm. A number of experiments 

 were performed to test the effect of fertilizing eggs whose develop- 



