EFFECT OF EXTRACTS UPON DEVELOPING EGGS. 9! 



Experiments were also made using- glycerine and chloroform 

 for solvents, but since chloroform appeared to be very difficult to 

 use, and since glycerine even in very small concentrations caused 

 a high degree of mortality in the cultures, no further work was 

 done at this point. 



ANALYSIS AND DISCUSSION OF RESULTS OBTAINED. 



The end result of the investigations described in this report is 

 that the larvae of Arbacia piinctnlata, and probably of Astcrias 

 forbcsii, contain substances which, when extracted in sea water 

 or other solvents, and zvfacn present in sufficient concentration, 

 retard the development of the eggs of the same species. 



This retardation was shown in most cases only in a slight de- 

 gree in the early cleavages, but more markedly in the later stages, 

 especially at the early non-motile blastula stage. There would 

 appear, then, to be certain periods at which the egg is more sus- 

 ceptible to the action of the extracts than at other times. 



It is interesting to note in this connection that Lyon ('02) 

 showed that eggs placed in a weak KCN solution gradually lose 

 their resistance to the KCN as development proceeds. At the 

 same time, there appeared to be certain periods at which the eggs 

 were more susceptible to the poison than at other periods. 



Child studied the effects of various chemical agents upon the 

 egg of the sea-urchin to prove the existence of axial metabolic 

 gradients as fundamental factors in the development of this form. 

 While it was not at all proposed to attempt in these investigations 

 a corroboration of Child's work, results in the controls in which 

 the agents used as solvents for the larval extracts were the same 

 as those which Child used, were similar, and many of the abnor- 

 mal types which he described were noted. 



Child 19 showed that the effect of KCN, C 2 H 5 OH, NH 4 OH, 

 NaOH, HC1, and CH 3 COOH was a differential inhibition mani- 

 festing itself in various deviations from the normal course of 



isa Lyon, E. P., " Effects of Potassium Cyanide and of Lack of Oxygen 

 Upon the Fertilized Eggs and the Embryos of the Sea-urchin (Arbacia punctu- 

 lata)." Am. Jouni. Physiol. Vol. VII., pp. 56-75, 1902. 



19 Child, " Larval Development in the Sea Urchin," Journ. of Morph., Vol. 

 XXVIII., 1916-17. 



