Sh'2 OF GENERATION GENERAL CHARACTER OF THE FUNCTION 



of the embryo ; whilst in others, only a portion is so segmented, the remain- 

 der being as it were a store of food which is gradually taken up in the pro- 

 cess of development. The former kind of egg consists, therefore, altogether 

 of germ yolk ; the latter of a small germ yolk, and a large food yolk. The 

 former has been called " holoblastic," the latter "meroblastic." The former 

 is found in Man and Mammals, Batrachians, Cyclostome Fishes, the lower 

 Crustacea, Arachnida and Mollusca, Annelids, Worms and Radiate animals; 

 the latter in Birds, Amphibia, Fishes, Cephalopods, and the higher groups 

 of Crustacea and Arachnida. In many of the lower tribes of animals, the 

 fertilization of the ova is accomplished without any sexual congress; the 

 spermatic fluid effused by the male, coming into direct contact with the ova 

 previously deposited by the female ; but in all the higher tribes, as in Man, 

 the spermatic fluid is conveyed into the oviducts of the female, so as to im- 

 pregnate the ovum shortly after it has quitted the ovarium, or even before 

 its final escape from it. 



2. Action of the Male. 



730. The Spermatic fluid of the Male is secreted by glandular organs, 

 known as Testes. Each of these consists of several lobules, which are sepa- 

 rated from each other by processes of the Tunica Albugiuea that pass down 



/.- 





US' m ( 



TTuniiin Test is, injected with rnereury as completely as possible; 1, 1, lobules formed of seminiferous 

 tiilirs; ', rete testis; 3, vasa eflerentia ; 4, flexures of the c tie rent vessels passing into the head; 5,5, of 

 the epididy mis ; G, body of the epididymis ; 7, appendix ; 8, cauda ; 9, vas deferens. 



between them, and also by an extremely delicate membrane (described by 

 Sir A. Cooper under the name of Tunica Vasrulosa) consisting of minute 

 ramifications of the spermatic bloodvessels united by areolar tissue. Each 

 lobule 'Fig. 306, 1 1) is composed of a mass of convoluted fnbiiH .^nnii/ifi r!, 



throughput which bloodvessels are minutely distributed. The lobule* differ 

 greatly in size, some containing one, and others many of the tubuli ; the 

 total number of the lobules is estimated at about 450 in each testis, and 

 that of the tubuli at 840. The walls of the tubuli are firmer than those 

 of similar gland-canals elsewhere; for outside the basement-membrane on 

 which the epithelium rests, they have a tolerably firm but extensible en- 



