353 



Cross Fertilization Among Fishes. 



By W. J. MoENKHAus, Indiana IIniveesity, Bloomington, Indiana. 



contents. 



Page 



Introductory 353 



Historical 354 



Methods 355 



Description of Crosses 356 



Summary of Experiments — 



Introductory 378 



Character of Impregnation 378 



Percentage of Fertilization 378 



Development 379 



General and Theoretical Considerations — 



Selective Fertilization 384 



Degree of Development and Systematic Relations 385 



Summary 391 



Literature Cited 392 



INTRODUCTORY. 



In the following pages I wish to record the more important results 

 of my experiments in the cross-fertilization of fishes. These have been in 

 progress more or less continuously since 1898. These experiments were 

 originally undertaken with quite another object iu view, namely, for inherit- 

 ance and cytological studies. A survey of available nearly related forms 

 was made that would successfully hybridize for variation and inheritance 

 studies. Anntlier jiurpose was the hybridization of forms with different 

 shaped clirniiios.'niH's. so thai" tlic liehavior of the latter could be followed iu 

 development. It soon devclopi'd lh.it the possibility of cross-fertilizing 

 fishes was wvy nun-h gi'eater than had liitlierto been supposed. This led 

 nie to seek nil jKissilile cnmliinatious of species of whatever relationship 



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