308 H. H. NEWMAN. 



curred but none of the most extreme types were noted. Those 

 in lot C showed the most pronounced abnormalities. Only a 

 few hatched and these were rather feeble. The remainder were 

 monsters belonging to a wide range of types, many showing 

 merely some defect in the circulation (string-hearts, enlarged 

 pericardia, no blood, etc.), others being defective in the head 

 parts, especially eyes, and others being defective chiefly in the 

 posterior parts. 



These two experiments were repeated many times and gave 

 substantially identical results each time. There can be no 

 question therefore that there is a very dose correlation between 

 the rate of development and the degree of normality of the embryos. 



When in homogenic crosses a slight increase in rate of develop- 

 ment is instituted the result is a supernormal FI hybrid type, 

 in which the difference is largely physiological, consisting of 

 greater activity and greater viability. When in the heterogenic 

 crosses there results a more or less pronounced retardation in 

 developmental rate (sometimes clearly seen in the early cleavage 

 stages) a subnormal type or monster is the result, which differs 

 from the normal not only physiologically in being non-viable 

 but morphologically in being defective in one or more parts. 



Both supernormal and subnormal types appear then to be cor- 

 related with an alteration in the normal rate of development. 



It is quite evident from numerous experiments (Newman, '15) 

 that the degree of retardation resulting from varous heterogenic 

 hybridizations is not a factor of the distance of the cross, for 

 some species of the same genus cross with poor success, and 

 some species of different orders of teleosts cross so as to produce 

 swimming larvae. This argues against the theory that foreign 

 sperm introduces toxins, since the protoplasm of distantly related 

 forms ought to be more toxic than that of near relatives. 



About all we can say then is that in introducing a foreign sperm 

 into an egg we either accelerate or retard the developmental rate of 

 the egg. In proportion as the rate is accelerated we get a super- 

 normal result, and in proportion as the rate is retarded, a sub- 

 normal result. 



That there is nothing specific about the effect of foreign sperm 

 upon the developmental rate of the egg is further shown by the 



