200 STUDIES IN GENERAL PHYSIOLOGY 



solution for a few hours with spermatozoa that had been 

 under the same conditions, only about one egg in a million 

 began to show some trace of segmentation, and as a rule this 

 segmentation remained in statu luiwmU, but was not accom- 

 plished. All these observations are totally different from the 

 phenomena described above. Eggs which had been fertilized 

 in normal sea-water, and which were put into the concen- 

 trated solution, after being brought back into normal sea- water 

 for from ten to twenty minutes segmented without any excep- 

 tion, and were able to develop into normal blastulae and plutei. 

 Eggs of this kind were still able to develop into normal 

 larvse after having been in the concentrated solution for four 

 to six hours. But eggs which l>cj\>rc impregnation had been 

 put into the concentrated solution together with spermatozoa, 

 and which four to six hours later were brought back into nor- 

 mal sea-water, reached only the first stages of segmentation, 

 if they segmented at all, and then stopped developing. I 

 never got a living larva from these eggs. From all these 

 facts I conclude that, the continual increase of the nuclei of 

 the impregnated eggs in the concentrated solution was due, 

 not to polyspermia, but simply to segmentation of the nucleus. 

 In these experiments bacteriological precautions are neces- 

 sary, as the water of the aquarium is liable to contain quan- 

 tities of spermatozoa. 



7. From the above I believe to have shown that by bring- 

 ing fertilized eggs of sea-urchins into more concentrated sea- 



O ' ' 



water we added 2 to 2.4 g. of NaCl to 100 c.c. of sea-water 

 -the segmentation of the nucleus proceeds, although more 

 slowly than under normal conditions, while no segmentation 

 of the protoplasm is possible. The fact in itself is of some 

 technical value, as it enables us to separate two processes 

 which nature generally produces together, or which hitherto 

 we had not the power to separate at desire. In regard to 

 our knowledge of segmentation, we see from this that the 



