286 HELEN DEAN KIM.. 



At 9 A.M. on the morning of August 9, the larv.r in tin- ] _> per 

 cent, solution were dying, and a number of giant embryos had 

 been formed by the fusion of two or more of the larvae: the 

 embryos in the y^ per cent, and in the -$-$ per cent, solutions were 

 apparently normal and were moving vigorously. All of the 

 larvae were dead on the morning of August 10, although the tro- 

 chophores in the control culture were still very active at this 

 time. Preserved material showed no abnormalities worthy of 

 note. 



As weak solutions of alanin did not seem to affect the early 

 development of the eggs adversely a second series of experiments 

 was made in which batches of Chcetopterus eggs were treated 

 with 4 per cent, and with 2 per cent, solutions of alanin as soon a 

 they had extruded their polar bodies. 



None of the eggs in the 4 per cent, solution segmented, and 

 sections of preserved material showed that the eggs had been 

 killed before the formation of the segmentation-spindle. When 

 cleavage began in the eggs of the control lot at n A.M. a very 

 few of the eggs in the 2 per cent, solution were dividing in an 

 apparently normal manner; in the great majority of the eggs 

 segmentation was very greatly delayed. After four hours only 

 a few eggs had reached the 4-cell stage, and in these eggs the 

 cleavage planes had come in very irregularly. An hour later 

 development had stopped entirely and the eggs were fusing into 

 large, irregularly shaped masses. At this time the eggs were 

 transferred into normal sea-water in the hope that segmentation 

 might be resumed, but although the eggs seemed to live for some 

 hours, none of them developed beyond the 4-cell stage. 



In microscopic preparations of eggs that had been in the 2 per 

 cent, solution of alanin for two hours before fixation only a very 

 few normal 2-cell stages were found, and the great majority of the 

 eggs contained a multipolar spindle with tin- chromosomes very 

 irregularly distributed along the spindle fibres. Material fixed 

 after the solution had acted for five hours showed that only the 

 first cleavage in any of the eggs was normal and that in most 

 eggs development had stopped at this point. Where further 

 division had occurred the blaMomcrcs were very irregular in 

 size and shape, and although hundreds of eggs were examined no 

 stage later than an 8-cell stage could be found. 



