614 STUDIES IN GENEEAL PHYSIOLOGY 



The eggs that had been in solution 2 had a large number of 

 blastulae and gastrulse. They were free from debris and 

 looked very much like those drawn in Fig. 150. The eggs 

 taken from solution 3 had very few blastulse. The latter, 

 however, were perfect, except that the single egg as a rule 

 produced more than one embryo. The majority of the eggs 

 were still in the morula stage. The next morning, forty- 

 eight hours after the treatment with the MgCl 2 solution, 

 each one of the three dishes contained perfect plutei. 

 Many eggs of solution 3 which the previous day were still 

 in the morula stage had in the mean time developed into 

 blastulse or plutei. This time the plutei were still alive on 

 the following day (seventy-two hours after the treatment 

 with the artificial solution). Their vitality was not much 

 less than that of the normal plutei which often died just as 

 early. I mentioned that I had put back the eggs from the 

 MgCl 2 solutions into normal sea- water at three different 

 intervals. Those taken out last gave the best results. It is 

 very obvious that the unfertilized eggs develop much more 

 slowly than the fertilized eggs. The latter reach the pluteus 

 stage at the proper temperature within twenty-four hours or 

 little more, while the unfertilized eggs reach the pluteus 

 stage after forty-eight hours at the same temperature. I 

 had the same experience in all my experiments with unfer- 

 tilized eggs. The eggs that had been left in normal sea- 

 water remained undeveloped and not one egg had a mem- 

 brane. One egg in a hundred was segmented after twenty- 

 four hours in 2 or 3 cells, but none developed further. 



Ninth series. This time I intended once more to repeat 

 my experiments ai?d at the same time make control experi- 

 ments of an altogether different character. I will first speak 

 of the repetition of the old experiments. The unfertilized 

 eggs of one female were put into the following two solu- 

 tions: 



