ii PRELIMINARY ESSAY ON GENERATION. 
of nouriHiment: the voice changes into a deeper tone ; the beard begins to appear ; the parts deftlned for generation are 
fuddeniy expanded; and the ieminal fluid fills the refervoirs prepared for it's reception. This fuperabundance is ftill 
more evident in the female : it difcovers itfelf by a periodic evacuation, which commences and terminates with the faculty 
of propagating ; by a quick encreafe of the brealls ; and by a change in the fcxual parts. 
' I conceive, then, that the organic particles fent from all parts of the body into the tefticles and feminal veffels of the 
male, and into the ovarium of the female, compofe the feminal fluid ; v/hich, in either fex, is a kind of extraft from the 
different parts of the body. Thefe organic particles, inftead of uniting and forming an individual, fimilar to that in vvhofe 
body they are contained, as happens in vegetables and fome imperfeft animals, cannot accomplifli this end without a mix- 
ture of the fluid of both fexes. When this mixture happens, if the organic particles of the male exceed thofe of the female, 
the refult is a male ; but, if thofe of the female are moll abundant, a female is generated. 1 mean not that the organic 
particles of the male or of the female could fmgly produce individuals : a concurrence or union of both is requifite to ac- 
complilh this purpofe. Thofe fmall moving bodies, called fpermatic animals, which, by the afliftanceof the microfcope, 
are feen in the feminal fluids of all male animals, are, perhaps, organized fubitances proceeding from the individual 
which contains them; but, of themfelves, they are incapable of expanfion, or of becoming animals fimilar to thofe ia 
whom theyexift. That there are flmilar animalcules in the feminal fluids of females, is a circumllance which has oftea 
been difputed, but may neverthelefs be proved. 
* The ancients, indeed, were fo confident of the exiftence of a feminal fluid, that they difiSnguiflied the two fexes by 
their different modes of emilfion : ^od infra fe femen j acit , fcemina -vocatur ; quod in hac jacit, ?nas. Arift. de Animal. 
But thofe phyficians who attempt to explain generation by eggs,; or by fpermatic animalcules, infifi; that females have 
no particular fluid ; that the mucusifi"uingfrom the parts has been miftaken for a feminal fluid ; and that the opinion of 
the ancients on this fubjeft is deftitute of foundation. This fluid, however, does exifl ; and the doubts concerning it have 
arifen folely from attachment to fyftem, and from the difficulty of difcovering it's refervoir. The fluid which is feparated. 
from the glands about the neck and orifice of the uterus, has no vifible refervoir; and, as it flows out of the body, it is 
natural to think it is not the prolific fluid, becaufe it cannot operate in the formaiion of the fcetus, which is performed 
within the uterus. But, if a little of the male fluid enters the uterus, either by it's orifice or by abforption, and meets 
with the fmalleft drop of the female fluid, it is fufHcient for the purpofe of propagation. Thus, neither the obfervations 
of fome anatomifts, who maintain that the feminal fluid of the male can have no admiffion into the uterus; nor the op- 
pofite opinion maintained by their antagonifts ; have any influence on the theory we are endeavouring to eltablifli. 
' But the ftrongefl: proof that the femen of both fexes conduces to propagation, arifes from the refemblance of children 
to their parents. Sons, in general, referable their fathers more than their mothers; and daughters have a greater re- 
femblance to their mothers than their fathers ; becauie, with regard to the general habit of body, a man refembles a man 
more than a woman ; and a woman refembles a woman more than a man. But, as to particular features or habits, 
children fonietimcs referable the father, fometimes the mother, and fometimes both. A child, for example, will have the 
eyes of the father, and the mouth of the mother; or the complexion of the mother, and the ftature of the father. Of 
fuch pha;nomena it is irapofiible to give any explication, unlefs we admit, that both parents have contributed to the for- 
mation of the child, and confequently, that there has been a mixture of two ferainal fluids.' 
Having endeavoured to place the fyftem of this eminent writer in an impartial light, we mufl; briefly advert to the 
objeftions that other hypothetical enquirers have urged againft it. 
In the firft place, it has been faid, that it is impoffible to conceive organical fubflances without being organized ; and 
that, if deftitute of organization themfelves, they could never make an organized body, as an infinity of circi s could 
never make a triangle. It has been objci^lcd, that it is more difiicult to conceive the transformation of thefe organic 
particles, than even that of the animal whofe growth we are enquiring after; and, confequently, that this fyftem endea- 
vours to explain one obfcure thing by another ftill more obfcure. 
It has alfo been farther maintained, that thefe little animals, which thus appear fwimming and fporting in a'moft every 
fluid, when microfcopically examined, are not real living particles, but fome of the more opaque parts of the fluid, that 
are thus encreafed in fize, and feem to have a much greater fliare of aftivity than they aftualiy pofleis. for the moricn 
being magnified with the object, the fmalleft degree of it will appear very confiderable; and a being almoft at rel! m y, 
by thefe means, be apparently put into violent aftion. Thus, for inftance, if we obferve the fails of a windmill moving at 
a diftance, they appear to go very flow; but, if we approach them, and thus magnify their bulk to our eye, they turn 
round with rapidity. A microfcope, in the fame manner, ferves to bring our eye clofe to the objeft, and thus to enlarge 
it ; and not only to encreafe the magnitude of it's parts, but alfo of it's motion. Hence, therefore, it would follow, that 
thefe organic particles which are faid to conftitute the bulk of living nature, are but mere optical illufions ; and ihat the 
fyftem founded on them muft likewife be illufive. 
On iubjefts where certainty cannot poflibly be obtained, the mind frequently becomes bewildered ; and in the fearch 
of truth, which it cannot recognize even when found, lofes itfelf in boundlefs fcepticifm, or endlefs conjeflure. Happily, 
however, for mankind, the moll abftrufe enquiries are generally the moft ufelefs. Inftead, therefore, of balancing ac- 
counts between fexes, and attempting to sfccrtain to v/hich the bufincfs of generation moft principally belongs, it will be 
more inftruftive, as well as entertaining, to begin with animal nature from it's earlieft retirements and evanefcent 
outlines, and to purfue the incipient creature through all it's changes, till the period of it's coming forth perfeft in 
it's kind. 
Animals have ufuallv been diftinguiflied, with regard to their manner of generation. Into the oviparous and vivi- 
parous kinds; or, in other words, into thofe which bring forth an egg, which is afterwards hatched into life; and thofe 
which brino- forth their young alive and perfeft. In one of thefe tv/o modes all animals v.'cre fuppofed to have been pro- 
duced, and all other kinds of generation were regarded as imaginary or erroneous. But later difcoveries have taught us 
to be more cautious in drawing general conclufions ; and have even induced many to doubt whether animal life may not 
be produced merely from puirefaclion. 
Indeed, the infinite number of creatures that feem to derive their birth from putrid fubftance?, and the variety of 
minute in fefts feen floating in liquors, by the alfiftance of the microfcope, appear to favour this opinion. E ufton cbferves, 
that there are perhaps as many beings, which either live or vegetate, produced by a fortuitous afl^emblage of organic 
particles, as by a conftant and fucceflive generation. ' It is to fuch produftions,' continues he, ' that we ougnt to 
apply the axiom of the ancients, corruptio u.iius , generaiio altcrius. In the corruption, the fermentation, or rather m the 
reiblution of animal or vegetable fubftances, v.'e find real animals, capable of propagating their Ipecies, though they were 
not themfelves produced in this manner. Thefe varieties are more extenfive than we imagine. Though it be right to 
generalize our ideas, to aflemble the effffts of nature under one point of view, and to clafs her proouftions; yet num- 
berlefs lhades, and even degrees, in the great fcale of being, will always efcape our obfervat:on.' 
But whether we admit or difallow the truth of equivocal generation, it is certain that the former diftinftions of gene- 
ration were too limited : for we find many animals produced neither from the womb nor from the ftiell, but merely from 
cuttings; fo that to raultiply life in fome creatures, it is fufficient to multiply the diffeflion. This being the fimpleft 
method of generation, and that in which life feems to require the fmalleft preparation for it's exiftence, we fhall begin 
with it, and thus proceed from the meaneft to the moft elaborate. 
The earth-worm, the millipedes, the marine-worm, and many other infefts belonging to the watery element, may be 
multiplied by being cut in pieces: but, of all other cxiftcnces endowed with this extraordinary method of propagation, 
the polypus is the moft remarkable ; and from hence we fnall feleft our defcription. 
The'ftrufture of this creature may be compared to the finger of a glove, open at one end, and fliut at the other. The 
clofed end reprefents the tail of the polypus, with which it fixes itfelf to any fubftance it happens to approach ; the open 
end may be compared to the mouth ; and, if we conceive fix or eight fmall firings ifl'uing from this end, we flrall have a 
diftindl idea of it's arms, which it can ereft, lengthen, and contracf:, at plealure, like the horns of a fnail. 
The polypus is extremely voracious, and makes ufe of it's arms to catch and entangle futh miuu e infers as come 
within it's reach. It lengthens thefe arms feveral inches, keeps them feparated from each other, <.nd thus occupies 
alaroe fpace in the water, where itrefidcs. Thefe arms, when extended, are as fine as threads of iilk, and polTeis a n. ft 
exquifite 
