32 HELEN DEAN KING 



with ova which insure that ova of different species floating in the 

 sea shall each be fertilized by spermatozoa of the same species, so 

 that to grant there is still more delicate chemotaxis at work is not 

 an illegitimate but is indeed a reasonable supposition." Castle 

 ('03) also postulated selective fertilization in the elaboration of 

 his Mendelian theory of sex-determination. 



The one attempt that has been made to test the hypothesis of 

 selective fertilization (Morgan, Payne and Browne, '10) seemed to 

 indicate that the egg is fertilized by the first spermatozoon that 

 strikes it 'head-on,' but the conditions under which the obser- 

 vations were made were so abnormal that no definite conclusions 

 from them were possible, and even Morgan ('11) states that the 

 evidence is 'admittedly insufficient.' 



An earlier experiment that has a bearing in this connection seems 

 to have been overlooked and therefore needs to be noted here. 

 Marshall ('10) injected into the vagina of a pure-bredDandieDin- 

 mont bitch a mixture of seminal fluid taken from a pure-bred dog 

 of the same species and from a mongrel terrier of unknown an- 

 cestry. Fifty-nine days later the bitch littered, producing four 

 pups which were much alike. One of the pups died early, but 

 as the other three developed into mongrels which resembled the 

 terrier sire there was little doubt but that all four puppies were 

 mongrels. Marshall cites another case in which a Dandie Din- 

 mont bitch copulated with a dog of the same breed and two days 

 later with a Scotch terrier. The bitch littered three pups ; on e 

 was pure Dandie Dinmont, the other two half-bred Scotch terriers. 

 These cases, according to Marshall, were indicative of a 'selec- 

 tive' on the part of the ova of the pure-bred bitch to "conjugate 

 with dissimilar rather than with related spermatozoa." 



I have recently been making a series of experiments somewhat 

 on the order of those cited by Marshall, and the results obtained 

 indicate a very strong tendency on the part of the ova of the al- 

 bino rat to conjugate with spermatozoa from the wild gray rat 

 rather than with the spermatozoa of the albino rat, although under 

 the conditions of the experiment, details of which will be pub- 

 lished later, the advantage in every case was with the spermato- 

 zoa from the albino male. If fertilization can be selective in such 



