EXPERIMENTS WITH THE EGGS OF MOLLUSCS 269 



without segmentation. Kostanecki 1 found this in his experi- 

 ments with Mactra and the writer confirmed this for Lottia. 

 It must be remembered, however, that these are only short- 

 comings of the method, and it was therefore to be expected that 

 different methods would give different results. 



The writer did not succeed in causing artificial partheno- 

 genesis in the eggs of Cumingia, a mollusc at Woods Hole, by 

 any of the older methods, but Wasteneys and he succeeded in 

 not only causing these eggs to develop, but also to develop with 

 normal segmentation by treating them with ox blood. The 

 method used was as follows. The eggs were sensitized to the 

 effects of serum by placing them for from two to four minutes 

 into a 3/8 m solution of strontium chloride. They were then 

 placed for five minutes in ox serum rendered iso tonic with sea- 

 water and diluted with an equal part of a m/2 solution of 

 NaCl+CaCl 2 +KCl. After having been freed from all traces 

 of serum by repeated washing in a Ringer solution, they are 

 transferred for sixty minutes into hypertonic sea-water (50 c.c. 

 sea-water +8 c.c. 2^ m NaCl). Control experiments showed 

 that the treatment with serum is an essential factor in this 

 process. 2 



This latter experiment shows the close similarity of the 

 methods of artificial parthenogenesis in various groups of 

 animals. 



1 Kostanecki, "Zur Morphologie der kiinstlich parthenogenetischen Ent- 

 wicklung bei Mactra," Arch. f. mikroskop. Anat. u. Entwicklungsgesch., LXXII, 

 327, 1908. 



2 Loeb and Wasteneys, " Fertilization of the Eggs of Various Invertebrates by 

 Ox Serum," Science, XXXVI, 255, 1912. 



