149 



believed he was able to bring about in a given solution a division 

 of the nucleus of the Arbacia egg without a corresponding cytoplasmic 

 division. The results were so remarkable that they seemed worth 

 working over again, if only to confirm the observations. The experi- 

 ment consisted in adding 2 °/ additional sodium chloride to sea-water 

 and then placing fertilized eggs in the solution. I have tried the 

 experiment four times, twice on unsegmented eggs and twice on two 

 cell stages. I found as described by Loeb that so long as the eggs 

 remain in this solution, the protoplasm does not segment and that 

 when the eggs are returned to fresh sea-water they immediatly break 

 up into a greater number of blastomeres than is normal. That this 

 segmentation corresponds in any way to the normal stages I could 

 not verify as the process seemed to me too irregular. Loeb's account of 

 the nuclear phenomena also conveys an erroneus impression. Eggs put 

 into the salt solution come to rest both for the protoplasm and 

 the nucleus. A long series of stained preparations of eggs, taken 

 at stated intervals during their immersion in salt, and also after their 

 removal to fresh sea-water, show beyond question, that throughout all 

 the time of immersion in the salt solution the nucleus is at rest. Its 

 nuclear membrane disappears and the chromatin collects in one (or 

 two) small highly staining pieces. When the eggs are replaced in the 

 sea-water the nucleus then undergoes a rapid and irregular division 

 (fragmentation) arjd the nuclear pieces migrate to the periphery of 

 the egg. Later these become centers in the protoplasm to form 

 blastomeres. 



The phenomenon, as Loeb stated and as I can verify, has nothing 

 to do with polyspermy, since, as Loeb showed , the spermatozoa are 

 paralyzed at once by the salt solution. I found that by keeping sperma- 

 tozoa in the salt solution for two hours (the time used in my ex- 

 periments) they never recover again their ability to fertilize normal 

 eggs. Very few weak larvae come from eggs treated as 

 described above. 



II. 



A few experiments were made on the star -fish eggs (Asterias 

 Forbesii). When the eggs are removed from the ovaries, large nuclei 

 are found in all of them. If the eggs be capable of development, 

 these nuclei soon disappear and in the course of an hour two polar 

 bodies are extruded. These polar bodies are extruded from ripe 

 eggs whether spermatozoa have been added to the water or not. In 

 most cases only comparatively few eggs in a lot undergo the process 

 described above, due to the fact that most of them are not fully 



