304 
that happened to be spawning at the same time, and note the possibility and 
character of impregnation, the development of the hybrids and the fate 
of developing embryos. 
The writer wishes to express his sincere thanks to Prof. Charles B. 
Davenport for privileges enjoyed at the Miami Laboratory, Cold Spring 
Harbor; to Hon. Geo. M. Bowers and Supt. Francis B. Sumner for privileges 
at the United States Fish Commission Laboratories at Woods Hall, and to 
the trustees of the Elizabeth Thompson Science Fund for a grant that made 
it possible incidentally to gather some of the data included in this report. 
HISTORICAL. 
With one exception, to be noted later, it is possible to impregnate the 
eggs of any of the species tried, with the sperm of any other species tried, 
although they belonged to widely separated orders. Isolated instances of 
equally, or even more distinct crosses have been recorded. Appell6f (94) 
made the following crosses among fishes: 
Pleuronectes platessa & 
x 
Gadus morhua 
Labrus rupestris 9 
x 
Gadus morhua <j 
In each of these the species belong to distinct orders. A portion only of 
the eggs were impregnated. A few showed irregularities in cleavage, and 
were presumably polyspermic. The European Amphibia have been exten- 
sively hybridized by Pfliiger (S82) and by Born (83). The former succeeded 
in impregnating the eggs of Rana fusca with the sperm of both J'riton 
alpestris and Triton taeniatus, i. e., an Anuran with a Urodele. The seg- 
mentation, however, was irregular so that all the eggs were probably poly- 
spermic. Morgan (98) succeeded in impregnating the eggs of Asterias with 
the sperm of Arbacia. He obtained normal cleavage, the larvie developing 
to blastulee and gastrulie. His experiments were carefully repeated Dy 
Driesch (98) without result. Mathews (’01) believed Morgan’s results 
were due to parthenogenesis induced by shaking the eggs. Loeb (’03), work 
ing with the Pacific Coast Echinoderms, found it impossible under normal! 
condition to fertilize the eggs of Strongylocentrotus purpuratus with the 
