TUUULE RECTI OR STRAIGHT TUBULES. 175 



becomes " reduced " to half the number characteristic of the 

 cells of the species (page 36), so that when joined to the 

 female element, likewise reduced (page 39), the fertilized 

 ovum possesses the normal number of chromosomes (sixteen 

 in man). 



As the spermatozoa are endowed with the power of transmitting to 

 the offspring the characteristics of the parent, the process of spermato- 

 genesis is a link in the chain of heredity. The mode by which the 

 parent implants or involves his own characteristics within the minute 

 compass of a spermatozoon, so that the latter in its further develop- 

 ment reproduces its kind, is a biological question of great importance. 



The characters of the parent are either congenital (racial, inherited) 

 or acquired; the latter few in number, the former multitudinous. 

 Many biologists contend that characteristics acquired by an individual 

 subsequent to his conception and birth cannot be transmitted to his 

 offspring; but supposing it possible, what mechanism exists in the 

 genital organs by which the features of a distant part of the body can 

 be impressed upon spermatozoa developing in the testicle so as to be 

 carried on to the progeny ? Obviously the only channels by which 

 impressions or influences from other parts could be conveyed to the 

 testicle are the circulation and the nerves. The testes are amply sup- 

 plied with bloodvessels; not so well, perhaps, with nerves. We can 

 conceive how, in conditions of toxaemia or generally lowered vitality, 

 an impoverished or toxic blood could alter or lower the vitality of the 

 spermatogenic cells and thus convey a deteriorating tendency to the 

 offspring; and we are also familiar with trophic nervous effects; but 

 aside from these, the manner in which bodily features might become 

 impressed on the spermatogenic cells through nervous or circulatory 

 influences is obscure. 



Little is known likewise as to just how the congenital or inherited 

 features of the parent, the fixed and stable characters of the race, are 

 carried over from generation to generation. Amidst the vast multi- 

 tude and diversity of cells making up the body, what line of cellular 

 transmission of racial features connects the 'ovum, from which an 

 organism develops, with the ovules or spermatozoa of the next genera- 

 tion which after a time appear in the body of the parent ? 



Many biologists regard the cells into which an ovum develops as of 

 two fundamentally different kinds : somatic cells, making up the body 

 generally ; and germ-cells, to which the developmental powers of the 

 ovum are transmitted. According to this theory, the spermatogenic 

 cells of the testicle and the corresponding cells of the ovary are direct 

 descendants of the ovum through a succession of germ-cells (located 

 in the sexual glands), which have carried on, in isolated continuity as 

 it were, the reproductive potentialities inherent in the ovum. 



The tubuli recti or straight tubules: The convoluted tubules 

 converge toward the mediastinum testis, and at their proximal 



