236 SUMMARY OF CURRENT RESEARCHES RELATING TO 



In the male the scrotum is the equivalent of the labia majora, and 

 the closed urethra is represented by the labia minora and urethra of 

 the female. Attached to the testes is the hydatid testis, the rudimentary 

 representative of part of the opposite sex-duct element, the fimbriated 

 end of the Fallopian tube. The testis develops its framework on the 

 genital ridge of the Wolffian body, utilizes parts of the ducts for its 

 tubular portion, taking the Wolffian duct proper for its vas deferens. 



The most pronounced differences between the sexes in man are : — 

 1. The pelvic position of the ovaries, the testes being extra-abdominal 

 and in the scrotum. 2. The fully developed and permanent round 

 ligaments and ovarian ligaments, represented in the male foetus in 

 the earlier months by the transient stages of the gubernaculum and 

 testicular caudal ligament. 3. A split condition of the labia majora 

 and minora, comparable with 'the early stages in the male, leading up to 

 the formation of the scrotum, the closure of the spongiosum, and the 

 formation of the urethra. 4. A loss in the female of the middle 

 segments of the Wolffian duct and of the greater part of the Wolffian 

 body, but retention of a part of it as epoophoron and paroophoron, as 

 well as of the lower ends of the .Wolffian ducts, to form the hymen. 



The next step in the author's argument is to show that the genital 

 tract is "segmental," or made up of separable items which may be 

 awanting individually. These correspond to unit characters or groups 

 of unit characters. Thus the male system consists of kidney, ureter, 

 epididymis, vas deferens, vesicular seminales, and gubernaculum testis, 

 with hydatid testis and prostatic utricle as non-potent elements. 



In the typical human female genital tract there may be forty 

 possible " segments," and four non-potent. In the male there may be 

 twenty-seven potent, and six non-potent. These conclusions are based 

 on the study of exact losses in atypical urogenital tracts. 



" The human potent genital-duct tract and the opposite sex-duct 

 elements, constituting with other structures the typical sex-ensernble. 

 have a t maximum-minimum, i.e. probability relation, due to successive 

 polar-body losses of the autonomous determinants causal to adult results 

 at maturation, and are recorded in the germ-plasm." 



Mendel's unit characters are causally represented in the germ-cells 

 and their derivatives by Weismann's determinants. They are dis- 

 tributed in a probability ratio, and discontinuous variation is due to 

 losses in polar-body formation. In a sex-ensemble there is a maximum 

 of the duct-segment characteristic of the sex, and a minimum of those 

 of the opposite sex-duct element. Weismann's determinants are regarded 

 as molecules and ions, the former of which may be neutral when quiescent, 

 the latter positive or negative during mitosis aud maturation. In 

 mitosis there is a temporary persistence of negative and positive ions ; 

 in polar-body formation there is an ejection of ions. The former gives 

 rise to continuous variations, the latter to discontinuous variations or 

 mutations. 



Inhibition of Pigment.* — A. M. Banta corroborates previous work 

 (on Spelerpex), showing that phenols prevent the formation of black 



* Year-book, Carnegie lust. Washington, xiii. (1914) pp. 123-5. 



