THE DETERMINATION OF SEX. 



29 



ova was advanced, for example, by B. S. Schultze; but as the grounds 

 for his views are not admitted as correct, only its existence need be 

 noticed till more observations are forthcoming. 



IV. Numerous authors have attached great importance to the 

 process of fertilization as a determinant of the sex. 



One of the most crude positions has been that of Canestrini, who 

 ascribed the determination of sex to the number of sperms entering 

 the ovum. The more sperms the greater the tendency to male offspring. 

 It has, however, been shown by Fol, Pfluger, Hertwig, and others, 

 that "polyspermy," or the entrance of more than one sperm, is 

 extremely rare, — is, in fact, generally impossible; and when it does in 

 rare conditions occur, indicates a pathological condition of the egg- 

 cell, and tends to produce abnormalities. Pfluger diluted the seminal 

 fluid of male frogs, and found that no change resulted in the normal 

 numerical proportion of the sexes. The case of drones, furthermore, 

 where males are known to arise from unfertilized ova, is a familiar 

 example, exactly counter to Canestrini' s proposition, which may in 

 fact be dismissed as wholly untenable. 



V. Time of Fertilization. — With greater weight various 

 authorities have insisted upon the time of fertilization. Thus accord- 

 ing to Thury (1863), followed by Diising (1883), an ovum fertilized 

 soon after liberation tends to produce a female, while an older ovum 

 will rather develop into a male. As a practical breeder, Thury claimed 

 to determine the sex of cattle upon this principle; Cornaz and Knight 

 have both practically confirmed this; while Girou has pointed out that 

 female flowers fertilized as soon as they were able to receive pollen 

 tended to produce female offspring. Hertwig has also shown that the 

 internal phenomena of fertilization vary somewhat with the age of the 

 ovum at the time. Hensen is inclined to accept the general accuracy 

 of Thury' s conclusion, but extends it to the male element as well. 

 ' ' A very favorable condition in both ovum and sperm will probably 

 lead to the formation of a female." "According to its condition, a 

 sperm may either insufficiently corroborate the favorable state of the 

 ovum, or constitutionally strengthen an ovum less satisfactorily con- 

 ditioned." 



VI. — Age of Parents. — Hofacker (1823) and Sadler (1830) inde- 

 pendently published a body of statistics, each including about 2,000 

 births, in favor of the generalization that when the male parent is the 

 older the offspring are preponderatingly male; while if the parents be 

 of the same age, or a fortiori if the male parent be the younger, female 

 offspring appear in increasing majority. This conclusion, generally 

 known as Hofacker' s and Sadler's law, has received both confirmation 

 and perplexing contradiction. It has been confirmed by Gohlert, 



