“miniature animal—the germ—was carried 
not only a keen observer but a careful writer as well. 
oN Gas 
NEW YORK, FEBRUARY 9g, 1894. 
WE regret the delay inthe issuing of Scvence, which is 
due to its taking longer to install Tur Scimnce Press than 
was expected. Now that the new office isin working order 
we hope to make up for Jost time. 
CHARLES BONNETS IDEA OF THE DEVELOP- 
s MENT -OF THE CHICK 
Cartes Bonnet, the distinguished naturalist, was 
born in Geneva in 1720 and died in 1793. He worked 
assiduously with microscope and leis and devised many 
hew experinients on plants and aiiimals. He was a friend 
of Haller’s and stoutly maintained the latter’s doctrine 
that all the vital functions could be reduced to two— 
sensibility and irritability. His first important work was 
the investigation of the life history of aphides, and his 
Interpr etatioli of parthenogenesis was a great triumph to 
the oz7s¢s. Vhe process of development in his time was 
considered by many to be purely a proces of unfolding of 
a preformed germ which contained in miniature the future 
animal or plant. But the supporters of his idea were 
divided into two camps: the anzmalculists held that.the 
in the male 
seminal fluid to the proper matrix, where it found suitable 
nourishment and grew—~.c., unfolded. The ozzs¢s, on the 
? 
other hand, maintained that the germ existed in female 
and explained fecundation as a stimulus produced by the 
male fluid which furnished the first nourishment of the 
tiny germ. ‘The fact, then, that a female aphide could 
produce offspring without coupling with a male seemed to 
give the oyists a convincing argument. 
His works are interesting reading to-day, for he was 
To 
be sure, his facts are often meagre, and often the results 
of his or his contemporaries’ observations were insufficient 
‘to base the broad generalities upon in which he delighted; 
yet within the knowledge that he had he argued well. 
Who knows but what the student of a hundred years hence 
may smile at Weissman’s conclusions as we clo at Bonnet’s? 
In the following description of the development of the 
chick the reader should always keep this in mind and 
should as far as possible forget for the time much of the 
detail that has become known to us since improved 
microscopes and sections have been in use. ‘The selection 
translated below may be found in his ** Contemplation de 
la Nature ” (tome iv., pt. 1, chap. x.), published in 1764: 
. LA GENERATION—LE POULET. 
An egg not fecund has a yolk like an unfecund egg. 
The goodwives have known this all the time; and there is 
in this little fact, so well known, so little examined and 
so worthy of it, something which comes to throw a flood 
of light and has cleared away the shadows with which the 
great mystery of generation-has been enveloped. 
_continue to grow? 
Give all your attention to this: you are going to put 
your finger on an important verity. A membrane invests 
the yolk internally, and this membrane, which is only the 
continuation of that which covers the “gaia intestine of 
the chick, is common to the stomach, the pharynx, the 
mouth, to the skin and epidermis. Another membrane 
invests the yolk externally, and this membrane is only the 
continuation of that which covers the intestine: this 
unites with the mesentery and peritoneum. The arteries 
and veins which course through the yolk derive their 
origin from the mesenteric arteries and veins of the 
embryo. The blood which circulates in the yolk receives 
from the heart the impulse of its motion. 
The yolk is, then, essentially, an appendage of the 
intestine of the embryo, and together they form an 
organic whole. Therefore, in earliest times, the chick is, 
to some degree, an animal with two bodies: the head, 
trunk and the extremities compose one of these bodies; 
the intestines and the yolk form the other. At the end 
of incubation the second body is pushed within the first, 
and the two make but the one. 
But since the yolk exists in eggs which have not been 
fecundated, it follows necessarily that the germ is pre- 
existent to fecundation. This consequence stares one in 
the eyes: you come to see that the yolk is an essential 
part of the chick. You recognize the direct connection 
between the one and the other. The chick has not 
existed, then, withoutit. The membranes and vessels of 
it are only a continuation of those of itself. And how 
many other things there are which they have in common, 
which prove that they have never existed separately. 
The chick was, then, entirely in the egg before the 
fecundation. Then it owes not its origin to the liquor 
which the cock furnishes: it was defined en petite in the 
egg, prior to the commerce of the sexes. The germ, 
therefore, pertains exclusively to the female. 
The evolution or development proceeds by nutrition; 
you have seen it. Nutrition supposes circulation; you 
have seen it also. Finally you have seen that the heart is 
the seat of circulation. If it does make a circulation in 
the germ before fecundation you will admit at least that 
it is not sufficiént to perform the whole evolution which 
will render the germ visible, and which gives to all its 
parts, the form, proportions and arrangement which 
characterize the species. 
The germ cannot achieve its development in an egg 
which has not been fecundated, and incubation will only 
hasten its corruption. Yet what does it lack in order to 
It has all the organs necessary to 
evolution. It has taken on itself a certain increase, for 
eggs increase in virgin pullets; their ovaries contain them 
in various sizes. ‘The germ may grow, then. Why can 
it not develop completely? What secret force holds it 
back in the limits of invisibility? 
Growth depends upon the impulse of the heart. <A 
great growth depends upon a great impulse. ‘The heart 
of the germ which is not fecundated lacks this impulse. 
This demonstrates a certain resistance in the parts of 
the germ: In measure as it grows, this resistance in- 
