154 



ANIMAL AGGREGATIONS 



<o 



50 



60 



80 90 100 



Time I a Minutes 



Fig. io. — Showing the rate of cleavage in eggs of the sea urchin treated with acetone 

 extract from which the fat has been partially removed. Acetone (extract) minus fats, O . 

 Control, A. (From Peebles, 1929.) 



a 



I 



60 



70 80 90 100 



Time in Afinutes 



Fig. II. — A comparison of the results obtained by Peebles (1929) by using the filtered 

 alcoholic extracts of plutei (AA) with that of the precipitate (x, v). Ninety-seven per 

 cent ethyl alcohol (filtrate), A; 75 per cent ethyl alcohol (filtrate), A; control, O ; 75 

 percent ethyl alcohol (precipitate), X; 97 per cent ethyl alcohol (precipitate), V. 



