454 H. H. NEWMAN 



paper rather severely to task. The fundamental contention was, 

 however, scarcely touched upon by this critic, as was shown by 

 the writer (Newman '11) in a reply to Godlewski, in which the 

 minor inaccuracies in reporting the latter's results were admitted 

 and differences of interpretation were brought clearly upon a 

 controversial plane. 



It may then be considered as fairly well established that, at 

 least in the case of hybrids between closely related species, the sper- 

 matozoon exercises at first a slight and then a progressively more 

 pronounced iJifluence upon the rate of early development, but fails 

 to exercise any really hereditary function until the embryo begins 

 to differentiate tissues and organs. This point of view will, I 

 believe, be justified by the new data herewith presented. This 

 somewhat radical change of front on my part is the result of sev- 

 eral years of study and has been forced upon me especially by 

 the experiments about to be reported, the results of which are 

 herewith to some extent anticipated. 



In the Proceedings of the Indiana Academy of Science for 

 1910, published a year later, Moenkhaus reports upon an exten- 

 sive series of experiments dealing with "Cross fertihzation among 

 fishes." These range from extreme heterogenic crosses between 

 different orders of teleosts to those between closely related spe- 

 cies of the same genus. A useful summary of the chief facts 

 and conclusions is furbished and is here quoted : 



1. The eggs of any of the species of teleosts tried may be impregnated 

 by the sperm of any other species tried. 



2. The, number of eggs fertihzed is usually great, i.e., 75 per cent or 

 more. This bears no relation to the nearness of relationship of the two 

 species concerned. 



3. Normal impregnation is the rule, di- and polyspermy being the 

 exception. 



4. Development in its early stages proceeds normally, the deleteri- 

 ous effects of the two strange sex products upon each other showing 

 only at later cleavage or subsequently. 



5. The rate of development in the early cleavage stages is always 

 that of the egg species. Any effect of the strange sperm upon the rate 

 of development shows itself by slowing the process regardless of whether 

 the rate of the sperm species is faster or slower than the egg species. 

 A period of great mortality in the developing hybrids is gastrulation. 



