\ 



diaphanus. 



1 :: 



Menidia notata. 

 Menidia gracilis. 



1 



Gasterosteus bispinosus. 

 Apeltes quadracus. 



{ :: : 



Tautogolabrua adspersus. 

 Tautoga onitis. 



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 

 careful comparison of the final stages of a series of hybrids all of which 

 had the same species, Fundulus lieteroclitus, 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: 



r^ , f Fundulus heteroclitus X Fundulus majalis. 



Group 1 •, .. .. o rii,„h«n 



Group 2 



Group 3 



Group i 



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. 3 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 Gunner 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 e\ery case most of the eggs are impregnated. In the first group 

 the embryos largelj' 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 maj* 

 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 alnior- 

 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. 

 1'he blood vessels do not properly differentiate, the pericardial cavity be- 



