Artificial Parthenogenesis in Thalassema Mellita 103 



I was greatly struck with the marked difference in results observed 

 when the strength of the solution or the duration of the immersion 

 was varied by a very slight degree. For example, in a given experi- 

 ment 60 per cent of the eggs developed into actively swimming 

 trochophores, which could not be distinguished from normal 

 larvae, after five minutes' exposure to the following solution: 15 



cc. ^ HCl +85 cc. sea-water. Another lot of eggs from the same 



female, treated with the same solution, but for 6 minutes instead 

 of 5, yielded only about 5 per cent that underwent any develop- 

 ment at all, while in none of the eggs did this proceed beyond the 

 early cleavage stages. Here a difference of but one mmute m 

 the time of exposure gave rise to a profound difference in the 

 result, in the one case the solution being adequate to initiate the 

 developmental processes in a majority of the eggs, which then pro- 

 duced apparently normal larvae, while in the other case only an 

 abortive early development was induced in a very few eggs. Such 

 differences, however, in the relative proportion of larvae were by 

 no means constant; in Nos. 15 and 16 of the table it is seen that a 

 difference of one minute in the exposure to the same solution of 

 acetic acid had no effect upon the percentage of larvae obtained. 

 The following table illustrates a similar variability in cases 

 where the duration of immersion was constant, but the solutions 

 differed very slightly in the degree of concentration: 



