ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 681 



fere nee in the degree of dissociation is responsible for the 

 result. A second typical difference between the Arbacia 

 egg and the Chsetopterus egg consists in the fact that the 

 latter can be caused to develop by a small addition of HC1 

 to sea- water. Any other inorganic acid would probably act 

 in the same way, as the addition of a small amount of Cl ions 

 has no such effect. This small addition of acid diminishes 

 or neutralizes the alkalinity of the sea-water, but I have 

 failed to test whether the latter is rendered acid. 



The same treatment does not cause the Arbacia eggs to 

 develop beyond the two- or four-cell stage, even if they are 

 left in the solution for twenty-four hours. I have made a 

 number of new experiments this summer, but I have only 

 been able to confirm the experiments mentioned in a former 

 paper. 1 



I have pointed out that the experiments on artificial par- 

 thenogenesis force us to assume that the influence of the 

 spermatozoon upon the development and the transmission of 

 the qualities of the male depend upon different constituents 

 of the spermatozoon. On the basis of this assumption the 

 possibility of a successful hybridization between animals as 

 far apart as Worms and Echinoderms might be considered. 

 If we could cause the egg of Chsetopterus to develop by 

 treating it with KC1 and at the same time force the sperma- 

 tozoon of an Arbacia (or a similarly distant animal) to enter 

 into the egg, we might carry Echinoderm qualities into an 

 Annelid egg. 2 But in all my attempts at thus crossing the 

 female Chsetopterus with the male Arbacia perfect trocho- 

 phores without Echinoderm characteristics resulted. Al- 

 though the problem may not be capable of solution in these 

 two forms, I think that the experiments on artificial par- 



1 Part II, p. 576. 



2 Provided the spermatozoon of the Echinoderm contains no poison for the 

 Annelid egg. 



