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STUDIES IN CYTOLOGY 393 
eges may be obtained than if the transfer be made at any other 
time. 
It should be remembered that Hindle and I have worked with 
different eggs and that the processes are not necessarily exactly 
the same in both. I am inclined to believe, however, that the 
greater opacity of the Strongylocentrotus egg has prevented an 
observation similar to the one described here. 
In practice I found it convenient to divide the eggs into two 
portions as they were removed from the butyric acid mixture, 
placing those removed during the interval one and one-half to 
two minutes in one dish and those removed during the interval 
two to two and one-half minutes in another. Sometimes one 
lot, sometimes the other was better. In the work I used finger- 
bowls of about 400 cc. capacity. Probably the greatest advantage 
accruing from the use of the NaOH was that of being able to 
use smaller amounts of sea water and thus concentrating the mass 
of eggs. 
A considerable number of experiments for the determination 
of the most favorable hypertonic sea water were made. Theo- 
retically it would seem as though a hypertonic solution containing 
all of the salts of sea water might be more favorable than sea 
water increased in one salt only. However, neither the hyper- 
tonic solutions made by the evaporation of sea water, nor the 
use of hyper molecular Van’t Hoff solutions offered any advan- 
tages over the solution mentioned above. 
It seems scarcely necessary to note that the experiments were 
carried out with extreme care. Sterilized dishes and pipettes, and 
sea water heated to 70° C. cooled and filtered, were used through- 
out the work. Controls to indicate whether chance fertilization 
had taken place were kept throughout. 
My observations on the external and internal changes in the 
egg agree, except as above noted, with the descriptions of Loeb, 
Hindle and Wilson, and therefore need no discussion here. 
At first thought it might seem that after the exceedingly careful 
work that has been done on the cytology of artificially partheno- 
genetic Toxopneustes eggs nothing would be gained by a further 
study of such eggs. It must be remembered however, that the 
