ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 681 
ference in the degree of dissociation is responsible for the 
result. A second typical difference between the Arbacia 
egg and the Chetopterus egg consists in the fact that the 
latter can be caused to develop by a small addition of HCl 
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.’ 
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 Cheetopterus to develop by 
treating it with KCl 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.’ But in all my attempts at thus crossing the 
female Cheetopterus 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- 
1Part II, p.576. 
2Provided the spermatozoon of the Echinoderm contains no poison for the 
Annelid egg. 
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