389 
In order to obtain a somewhat more definite idea of the influence of a 
strange sperm upon the developmental processes, I have made a somewhat 
eareful comparison of the final stages of a series of hybrids all of which 
liad the same species, Fundulus heteroclitus, for the female but different 
species for the male, these latter varying in their nearness of blood relation- 
ship to the egg species. ‘These males fall into four separate groups of two 
species each. The male species in each group are closely related, but the 
different groups vary in their relationship to the egg species from that of 
the same genus to that of most widely separated orders. These groups are 
as follows: 
Groep 4 { Fundulus heteroclitus x Fundulus eae 
Group2 { ; Liena Cemee 
Group 3 | “ Rane oe 
ere. | reece 
In group 1, Fundulus majalis and Fundulus diaphanus will hybridize 
and bring their development to hatching. The same is true of the two 
species of Menidia in group No. 2. In group No. 8 the two species of 
sticklebacks will cross and hatch, although I have been able to rear the 
embryos for only a very short time. The Cunner and Tautog of Group 
No. 4 will likewise cross and, although many abnormalites occur, some of 
the embryos will hatch in a normal manner. When, however, these forms 
are crossed with Fundulus heteroclitus very divergent results are obtained, 
although in every case most of the eggs are impregnated. In the first groun 
the embryos largely hatch and may be reared. Among the normals may 
be found various abnormalities, but these are relatively rare. In the re- 
maining groups the embryos never hatch, although in some cases may 
remain Alive in the egg for three or four weeks. But each of these groups 
go to a characteristic stage of development and show characteristic abnor- 
malities. In all of the last three groups the mortality is great during | 
the period from the formation of the germ ring to the closure of the 
blastopore. 
In group 2 a varying number may go far beyond this stage forming 
normally the early stages of the eye, ear, heart, notocord, somites, etc. 
Although the early stages in the formation of these organs may be nor- 
mal, it soon becomes apparent that the further processes becomes aborted. 
The blood vessels do not properly differentiate, the pericardial cavity be- 
