GENERATION. 



facts, wliicli determine tlic order of arrangement ; while living The origin of the germs, and the mode of iheJr exiftcncr 

 bodies are compofed of numerous fibres or plates, heterogene- in the female ; whether tliey are originally formed in all 



ous in their conipofilioii, diverfified in their conligvnations 

 and dellined to particular fituations, fo that they can only 

 be in one place, and between other dctcrmiiK-d fibres or la- 

 mellx. Moreover, living bodies, lionevcr Imall they may be, 

 pofrefs all their parts from the hrft moment of their exillencc; 

 thev grow, not by the addilioii of new layer:;, but by the 

 fometimes uniform, and fometimes irregular developemcnt of 

 parts, all of which exilled previoufly to any fenlible growth. 

 The onlv eirciimftance belonging to all kinds of generation, 

 and conleqnently the only edential circumflance in the pro- 

 cefs is, that every li\ing body, at the firll periods of its fen- 

 fible exiftenee, is attached to a larger body, of tlie fame fpe- 

 cies with itfelf, that it makes a part of this larger body, and 

 is noiu-ifhcd by its juices for a certain length of time. Its 

 fubfequent feparation conflitutes its I'lrlh ; wliich maybe 

 produced fmiply from th.e life of the larger body, and the 

 confequent developcment of the fmaller, N.itlr.uit the aid of 

 any occafio}ial caufe. Thus, in its efleiice, generation, as fa- 

 ns we can underiland it, is only the appearance of a fmall 

 organized bod^' upon or in lome part of another and larger 



their parts in each individual by any vital procefs, or are all 

 pre-eKillent, being inclofed in each other, or whether they 

 are difi'eminated through the body, and require a coneourfe 

 of circumllances to bring tin m into a fituation favourable for 

 their developemcnt, are (itiellions, which it is utterly impof- 

 fiblc for us to decide in the prolent Hate of our knowledge. 

 Thcfc points have for along time been agitated by phyholo- 

 gills ; but the difcufTion leems now to be abandoned by 

 univirfal confent. 



The combination of the fexes, and the mode nf fecun- 

 dation, are fubji-6l to great variety. In fome inilances, the 

 two fexes are united in the fame individual, and fecinidation 

 is aceompliftied without any extraneous aid ; fuch are the 

 hermaphrodite and mono'icous plants, the acephalous mollul- 

 ca, and the cchlnodermato\is animals. In others, each indi- 

 vidual pofTefies botli fexes, but requires the afllftance of an- 

 other, which it fecundates, and by wliich it is fecundated. 

 Tliis is the cafe with the gailcropodous molluica, and with 

 (everal worms. There are diftincl individuals, male and te- 

 male, in other claffes ; as, for inflance, in the dio'icous plants, 



one, from which it will be feparatcd, at the expiration ot a in all animals, v.'hich have a vertebr.il column. In thecephalo- 



•certain period, in order to adumean independent and ifolat- podous and fome gafleropodous moUufca, in fome worms, i« 



■ed exiftcnee. All the acls or organs, which co-operate in the crullacea, and in inhcis ; ia Ihort, in the far largell por- 



.the procefs, in a certain clafHs of organized bodies, are only tion of the animal kingdom. 



accelfary to this primary lunclion. When the function is Fccumlclion is accomplilhed in plants by means of a liquor 



thus reduced to its moll fmiple ftate, it conftitutes \.\Kgemmi- contained in Imall capfules, which rcfemble a fine powder in 



parous, or generation by Ihoots. In this way buds are form- appearance, lodge on the female organs, and, burltlng, depo- 



cd on trees, and developed into branches, which will form fit their contents. In animals, the liquor is always applied 



future trees, by means of flips or cuttings. The polype immediately upon or about the germs ; and in many cafes 



(hydra) and the fea anemone (atlmia) multiply in this man- it is not brought in contaft with the ova, until they have 



ner ; fome worms are propagated by a divifion of their body, been laid, as in the bony and oviparous filhes, and the cepha- 



and muft therefore be arranged in the fame divifion. This lopodous mollufca : here the males and females have no com.- 



mode of generation requires no diftinftion of fex, no copu- 

 lation, nor any particular organ. Other modes of genera- 

 tion are accomphfiied m appropriate organs : the germs ap- 

 pear in a definite fituation of the body, and the alfiftance 

 of certain operations is required for their further develope 



meree. Sometimes, as in the frog and toad, copulation is 

 neceflary in order to determine the difcharge of the ova and 

 femen, but fecundation is ftlll performed out of the body. 

 Laftly, in the great majority of inilances, the femlnal liquor, 

 introduced by the male into the body of the female, fecun- 



ment. Thele operations conflitute_/('fun(/rt/;on, and fuppofe dates the ova before they are laid. This is the cafe in the 

 the exiflence of fexual parts ; which may either be feparate mammalia, birds, moll reptiles, and fome filhes, in thf' hernia- 

 or united in the fame individual. The fecundated or fecun- phrodite gafleropodous mollufca, in the cruftaccaand infefts. 

 dable fex, in which the germ is found, is the female ; and The union of the two rexes,or the adl oy wliicl; this is accom- 

 the fecundating fex, the affiflance of which is necelFary for plilhed, is called copvlaUon. In all the laft-mentloned orders 

 the complete developcment of the germ, is tlie male. The ova may be dlfcharged without previous copulation, as in the 

 officr of the latter is that of furnilhing the fecundating or preceding ones. But they receive no further dcvelopement ; 

 ■femlnal fluid : but the manner in v/hlch that contributes to nor can they be fecundated when thus voided. The effedl 

 the developcment of the germ, is not yet fettled by phyfiolo- of a fmgle copulation varies in its degree ; it ufually fecun- 

 gifts. Some, forming their opinions from the human fubjedl dates one generation only, and produces one pregnancy ; 

 and the niammalia, where the germs are imperceptible before but fometimes, as in poultry, feveral eggs are fecundated, 

 fecundation, fuppofe that thefe are created by the m.-xturc of and afterwards dlfcharged fuccellively : Tlill, however, they 

 the male fluid, with that which they fuppofe to exifl in the only form one generation. In a very few inftances, one aft 

 female ; or that they pre-exifl in the male femen, and that of copulation fecundates feveral generations, which can pro- 

 the female only furnlflies them with an abode. Others con- pagate their fpecies without the aid of the male. In the 

 fult the a alogy of the other claffes cf animals, and of plant-lonfe (aphis) the fpecies has been continued through 

 plants. In feveral inilances, particularly in the frog, the eight generations from one copulation ; and in fome mono- 

 germ may be clearly recognized in the ovum of the female cuh, through twelve or fifteen. 



before fecundation : its pre-exillence may be inferred, in When the germ is detached from the ovary, its means of 



other cafes, from the manner in which it is organically con- exiilence may be more or lefs complete. In moil animals it 



nefted to the ovum, when it is firfl vifible. For it is agreed is accompanied by an organized mafs, to which it is connecl- 



on all fides, that the ovum cxifts in the female before fecun- ed by means of vetfels. The abforption of this fervcs for its 



dation, finco virgin hens lay eggs, &c. From this analogy, 

 thefe phyfiologiils conclude, that the germ pre-exifts in all 

 females ; and tU'.l the fecundating liquor is a tlimulus v/hlch 

 bellows on it an independent life, by awakening it, in a man- 

 ner, from the fpecies of lethargy, in which it would have 

 A>therwife conilautlv remained. 



nutrition and developcment, until the period of its indepen- 

 dent exiilence. It derives nothing therefore from the body 

 of the mother, from which it is leparated by coverings, va- 

 rylng in number and folidity. The germ, together with its 

 mafs of nourlfhment, andth? furroundlng mi mbranes, confti- 

 tutes an egg, or fviiin ; and the animals, which produce their 



young 



