274 CARL R - MOORE. 



(a) Not a single blastomere of the first cleavage of an egg 

 (a half-egg) isolated and left standing in normal sea-water at 

 room temperature, appeared entirely normal at the end of twenty- 

 four hours. 



(b) A few of these blastomeres, without further treatment, 

 segmented again and some many times. This cleavage was 

 often delayed some hours after treatment, indicating that 

 developmental processes were going on very slowly. 



(c) Not a single normal larva was obtained out of hundreds 

 of these isolated blastomeres inseminated seven hours or longer 

 after the treatment. 



(d~) These inseminated, apparently normal blastomeres did 

 not form a fertilization membrane. 



(e) Out of the hundreds of half-eggs that have been insemi- 

 nated less than 10 per cent, have ever segmented. It is just 

 possible that some of these cleavages have been due to activation 

 by spermatozoa, but the eggs had been so weakened that cleavage 

 was abnormal and never reached the swimming stage. But 

 beyond doubt most of these cleavages were due to the slow develop- 

 ment going on within the egg similar to (b) above. 



With these facts in mind is it not possible to account for the 

 results of Loeb without considering that his half- or quarter- 

 larva? came from the fertilization of the separated blastomeres 

 of the 2- and 4-celled stage? As pointed out above, eggs that 

 have remained standing for 24 hours after hypertonic exposure 

 do not produce membranes after insemination, that are rigid 

 enough to hold the blastomeres together; and in these experi- 

 ments, as well as in Loeb's, many dwarf and badly deformed 

 larvae can be seen in the culture but they do not come from the 

 fertilization of a half- or quarter-egg, but rather from an egg 

 that was fertilized and later lost cells. Numbers of swimming 

 forms can be seen trailing a comparatively huge mass of cells 

 after it, that have been lost from the egg itself and consequently 

 has resulted in a reduction in size. Even in the cultures pro- 

 ducing swimming larvae from the effects of the hypertonic solu- 

 tion alone, one encounters these half-, quarter-sized, and even 

 smaller swimming masses representing parts of eggs, but these 

 too are reduced in size from loss of cells during the division of a 



