MODES OF INHERITANCE IN HYBRIDS 453 



use of foreign sperm. On this score I took occasion to criticise 

 the position of Conkhn, Godlewski and others, who, on the basis 

 of the work done on echinoderm hybrids, had declared that the 

 early development of hybrids is purely maternal and that it is 

 only in stages later than the gastrula that the influence of the 

 spermatozoon begins to make itself felt. There was in my ex- 

 periments a real effect of foreign sperm on the rate of early devel- 

 opment and this effect was not due to a more speedy impregna- 

 tion of the egg membrane by the foreign sperm head, as was 

 shown by the experiment in which all spermatozoa in both hybrid 

 and control cultures were destroyed with distilled water within 

 less than five minutes after insemination. By this time all 

 spermatozoa had entered the eggs, those of the foreign and native 

 species having entered with equal promptness. 



These results were criticised by Godlewski ('11) because they 

 were not confirmed by cytological studies. He did not explain, 

 however, just what he meant by a cytological confirmation of 

 a statistical treatment involving many thousands of eggs, no 

 small sample of which could be expected to show anything of 

 value. On the basis of what seemed to be a demonstration that 

 foreign sperm actually effects a slight change in the rate of early 

 cleavage, the writer entered upon a general discussion of the 

 role of the spermatozoon in early development and came to the 1 

 conclusion that, in addition to initiating development, the pater- 

 nal germ plasm reacts almost immediately with that of the egg 

 so as to change the rate and character of metabolism and thus,' 

 accelerate or retard cleavage. Naturally the cytoplasmic organ- 

 ization of the egg imposes upon the young embryo certain mor- 

 phological restrictions, but in all those matters that have to do 

 with rate of chemical reaction the spermatozoon begins to exert 

 an influence as soon as fertilization occurs, as soon as the two 

 ontogenies are engrafted one upon the other. The work of 

 Godlewski, Baltzer and others, who had experimented with echi- 

 noderm hybrids, was cited by the writer in confirmation of his 

 conclusions and it is to be regretted that, in citing Godlewski's 

 results certain misstatements were made, for it was in response 

 to these inadvertent inaccuracies that Godlewski took the whole 



