614 STuDIES IN GENERAL PHYSIOLOGY 
The eggs that had been in solution 2 had a large number of 
blastule and gastrule. They were free from débris and 
looked very much like those drawn in Fig. 150. The eggs 
taken from solution 3 had very few blastule. 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, 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 
blastule 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, 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 ard 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: 
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