384 
he found a distinct acceleration in the later cleavage stages and subse- 
quently in the hybrids between Fundulus majalis, female x Fundulus 
heteroclitus, male. 
GENERAL CONSIDERATIONS AND THEORETICAL. 
SELECTIVE FERTILIZATION. 
In a general consideration of these experiments, perhaps the most 
striking fact that appears is the uniformity with which it is possible to 
cross-fertilize the various species of teleosts. The percentage of eggs fer- 
tilized is in practically all cases a high one—fifty per cent., and, in the 
majority of cases, seventy-five per cent. or over. When one reflects upon 
the reason for one’s astonishment at this, he finds it in the fact that we 
have all, those of us who ive given the matter any thought at all, allowed 
curselves to grow into the belief that there is a sert of specific affinity or 
adaptation existing between an egg and the spermatozodn of the same 
species. ‘This assumption may or may not be true. So far as the writer 
has been able to determine, there is extant no evidence that this is the 
case in the animal egg. A possible exception is to be found in the ex- 
periments of Dungern (01), who finds that in the eggs of the star- 
fish there is a substance which is poisonous toward the sperm of the se; 
urchin, but not vice versa. It is easy to see that under such conditions 
the spermatozoa of the starfish would be favored. 
On the other hand, we have experiments by Buller on all the groups 
of Echinoderms which seem to show that there exists no specific affinity, 
chemical or otherwise, between the egg and its own spermatozoon. 
The writer is elsewhere publishing a detailed account of his experi- 
ments on selective fertilization in fishes. It may be proper, however, to 
briefly call attention in this connection to a few of the results he obtained. 
First. The fact above stated, that among these fishes it is possible so 
uniformly to cross-fertilize the different species lends no support to the 
“specific adaptation” theory. Second, When a lot of Fundulus heteroclitus 
eggs are given a chance at a mixture of two sperm, one of which is their 
own and the other a strange species (Menidia, for instance), the eggs do 
not necessarily show any preference for their own sperm. In the case above 
mentioned, for instance, the great majority of the eggs prefer the Menidia 
sperm to their own. In other combinations the proportion is about equal. 
In still others the eggs may select more of their own sperm. The factor 
