ACTION OF THE MALE. 951 



conveys the fertilizing influence to the "germ-cell" (or embryonic vesicle' of 

 the ovule) after a different fashion (Fig. 236, c) ; still, however, fulfilling the 

 same essential purpose as that which the simple " conjugation" of the lowest 

 Algae effected, namely, the mingling of the contents of the "sperm-cell" and 

 "germ-cell," which takes place by transudation through the thin membranes of 

 the pollen-tube and of the embryonic vesicle. The germ-cell is here surrounded 

 by a mass of nutritious matter, which, with the embryo, constitutes the "seed;" 

 and it is upon this store, that the young plant subsists during the early stages 

 of its development. 



956. The " act of Generation" in animals may be said to combine the prin- 

 cipal features of the second and third of the above methods j for, as in the 

 higher Cryptogamia, the " sperm-cells" of Animals seem invariably to form the 

 self-moving filaments known as Spermatozoa j whilst the " germ-cells," instead 

 of being naked (as in the Cryptogamia), are surrounded (as in Flowering Plants) 

 by a mass of nutriment destined to serve for the early development of the em- 

 bryo ; this mass with its contained germ-cell being known as the ovule before it 

 has been fertilized, and as the ovum or egg after fecundation has taken place. 

 There is a great difference, however, among the different tribes of Animals, as 

 to the degree of assistance thus afforded to the embryo ; the general rule being, 

 that the higher the form which the embryo is ultimately to attain, the longer is 

 it supported by its parent. Hence we find the embryos of most Invertebrated 

 animals coming forth from the egg in a condition very much unlike their perfect 

 type, and only acquiring this after a long succession of subsequent alterations, 

 which frequently involve a complete change of form, or metamorphosis. In 

 Fishes, however, the embryo, though far from having completed its embryonic 

 development at the time of its emersion from the egg, does not differ so widely 

 from the adult type. In Birds, there is a provision for a much more advanced 

 development j the store of nutritious matter, or " yelk," being so large as to 

 allow the whole series of changes requisite for the formation of the complete 

 chick to take place before it leaves the egg. In the Mammalia, on the contrary, 

 the quantity of yelk contained in the ovum is very small, but the embryo is 

 only dependent upon it for the materials of its increase during the earliest 

 stages of its evolution ; for it speedily forms a special connection with the pa- 

 rent structure, by means of which it is enabled to receive a continual supply of 

 newly-prepared aliment, so as to be supported at the expense of this until far 

 advanced in its development. Some approaches to this arrangement are met 

 with among certain of the lower Animals, but it is only in the higher Mam- 

 malia that it is completely carried out \ and it is only in this class, too, that we 

 find a supplemental provision for the nutrition of the offspring after it has come 

 forth into the world. 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, that it may impregnate the ovum 

 shortly after it has quitted the ovarium, or even before its final escape from it. 

 With these general views, we shall now be prepared to examine into the his- 

 tory of the act of Generation in Man, and to consider the share which each sex 

 has in its performance. 



2. Action of the Male. 



95V. The Spermatic fluid of the Male is secreted by glandular organs, known 

 as Testes. Each of these consists of several lobules which are separated from 

 each other by processes of the Tunica Albuginea that pass down between them, 

 and also by an extremely delicate membrane (described by Sir A. Cooper under 



