EFFECT OF EXTRACTS UPON DEVELOPING EGGS. 



79 



Note. In this particular experiment the figures given under 

 cleavage rate are in terms of minutes which elapsed between in- 

 semination and the appearance of the first 2-, 4- or 8-cell stage. 

 It should be noted that the amount of extract used in this series 

 was relatively large. (pH significance discussed later in paper.) 



Later Development and Fate. The eggs in cultures A and A' 

 stopped at the 128-256-06!! stage, and a very general cytolysis 

 occurred. 



The eggs in B and B' developed into vigorous normal plutei. 



Conclusion. The table shows that there was a definite retarda- 

 tion at the second and third cleavages in the cultures containing 

 extract, and a complete arrest of development at the beginning 

 of the early non-motile blastula stage. 



Series I'J. 

 TABLE II. 



Note. In this experiment the figures given under cleavage, rate 

 are in terms of minutes which elapsed between insemination and 

 the presence in the culture of fifty per cent, of the stage indicated. 



Later Development and Fate. Development in cultures B, C, 

 and to a slight degree in A, was definitely retarded, especially be- 

 tween the gastrula and early pluteus stages. In the great major- 

 ity of cases the gastrulse did not become plutei at all. The eggs 

 in culture D were very much retarded ; in fact, few progressed 

 beyond the blastula stage, due probably to lack of oxygen in the 

 water, and possibly to a high concentration of carbon dioxide. 

 Many of the eggs in the controls developed into plutei. 



