INTERNAL CAUSES OF VARIATION 189 



maturation ; (3) the retention of the spermatozoa from the 

 first mating, and their action in successive fertilizations. 



As to the first, there is no scientific ground for assuming the 

 slightest effect of the spermatozoa upon the tissues of the 

 female. It is the ovum that is fertilized, not the female, as was 

 at one time supposed when fertilization was regarded solely as 

 a stimulus. 



As to the second, there is no ground for believing that the 

 nuclei of growing immature oogonia are in condition to unite, or 

 that they are capable of uniting, with the nuclei of other cells in 

 any capacity whatever. 



As to the third, there is every ground for believing that the 

 spermatozoa are not retained for any considerable time, else 

 successive births would occur from a single mating. Moreover, 

 as but one spermatozoon takes part in fertilization, the blended 

 effect of two sires is impossible. It is even impossible in multiple 

 births when two services are close together. If a litter of pigs 

 is the result of two matings by different sires, some may resemble 

 one sire and some the other, but none will resemble both. 



SECTION VIII INTRA-UTERINE INFLUENCES 



It is a widespread tradition that distinct characters, especially 

 abnormalities, may be impressed upon the individual while in utero 

 through the imagination or other strong mental impression of the 

 mother. It has even been held in the case of hens, which would 

 necessitate the exertion of the influence upon the ovum itself. 



The usual argument is that the intimate contact between 

 the mother and the fetus renders the latter peculiarly susceptible 

 to influences affecting the former. Thus marks and deformities 

 of all sorts are popularly attributed to unfortunate sights and 

 experiences of the mother before the birth of the young. Pecul- 

 iarly marked calves are said to owe their markings to the strong 

 mental impressions created by a steer or by other cows, and colts 

 are believed by many to owe their color not so much to the sire 

 as to the gelding mate that worked beside the dam while she was 

 carrying her young. Persons with whom the tradition is strong- 

 often display a blanket of a pleasing color before the eyes of the 



