$ 805. 
mass, and {s, therefore, quite unlike a proligerous 
disc. 
When these egg-like germs have attained the size 
of one one-hundred-and-fiftieth of an inch in di- 
ameter, there begins to appear distinctly the sketch- 
ing or marking out of the future embryo. This 
ketchi at first o ly-marked re- 
treatings of the cells here and there ; but these last 
soon b more pr from , and, 
at last, the form of an articulated embryo is quite 
prominent. 
During this time, the yellowish, vitellus-looking 
mass has not changed its place, and although it is 
somewhat increased in size, yet it appears other- 
wise the same. When the development has pro- 
ceeded a little further, and the embryo has as- 
sumed a pretty definite form, the arches of the 
segments, which have hitherto remained gapingly 
open, appear to close together on the dorsal sur- 
face, thereby enclosing the vitellus-looking mass 
within the abdominal cavity. It is this same vitel- 
loid mass thus enclosed, which furnishes the de- 
velopment of the new germs (which in this case 
would be those of the fourth colony, or D), and this 
germ development here commences with the clos- 
ing up of the abdominal cavity, and then the same 
processes we have just described are repeated 
THE INSECTA. 
465 
bathed, and which fills the abdomen of the parent. 
The conditions of development in this respect, are 
here, therefore, more like those of the Mammalia and 
the whole parent animal may be regarded in one 
sense as an individualized uterus filled with germs, 
—for the digestive canal with its appendages 
seems to serve only as a kind of laboratory for the 
conversion of the succulent liquids this animal ex- 
tracts from the tree on which it lives, into this fatty 
liquid which is the nutritive material of tae germs. 
Omitting the curious and interesting details of 
the further history of the economy of these Insecta, 
as irrelevant to the point in discussion, we will now 
turn to see: what view we should take of these pro- 
cesses, and what is their physiological interpreta~ 
tion. In the Grst place it is evident that the germs 
which develop these viviparous Aphides are not 
true eggs; they have none of the structural char- 
acteristics of these last,—such as a vitellus, a 
germinative vesicle and dot; on the other hand 
they are at first simple collections, in oval masses, 
of nucleated cells. Then again, they receive no 
special fecundating power from the male, which ig 
the necessary preliminary condition of all true 
eggs; and furthermore the appearance of the new 
individual is not preceded by the phenomena of 
, 43 is also the case with all true eggs 
The details of the development subsequent to 
this time, — the formation of the different systems 
of organs, &c., are precisely like those of the de- 
velopment of true oviparous Arthropoda in gene- 
ral; and although the ovoid germ has, at no time, 
the structural peculiarities of a true ovum,— such 
as a real vitellus, germinative vesicle and dot, yet 
if we allow a little latitude in our comparison and 
regard the vitellus-looking mass as the mucous, 
and the germ-mass proper as the serous fold of 
the germinating tissue, as in true ova; if this com- 
parison of parts can be admitted, then the analogy 
of the secondary phases of development between 
these forms, and true ova of the Arthropoda, can 
be traced to a considerable extent. 
These dary phases of dev t need not 
here be detailed, for they correspond to those de- 
ecribed by Herold, Kolliker, of the true ovum in 
other Insecta, and which, too, I have often traced in 
various species of the Arthropoda in general. 
When the embryo is fully formed and ready to 
burst from its capsule in which it has been de- 
veloped, it is about one-sixteenth of an inch in 
length, or more than eight times the size of the 
germ, when the first traces of development in it 
were seen. From this last-mentioned fact, it is 
evident that, even admitting that these germ-masses 
are true eggs, the conditions of development are 
*uite different from those of the eggs of the truly vivi- 
parous animals, for, in these last, the egg is merely 
hatched in the body instead of out of it, and, more- 
over, it is formed exactly as though it was to be 
deposited, and its vitellus contains all the nutritive 
material required for the development of the em- 
bryo until hatched. With the Aphididae, on the 
other hand, the developing germ derives its nutri- 
tive material from the fatty liquid in which it is 
Therefore, their primitive formation, their develop- 
ment and the preparatory changes they undergo 
for the evolution of the new individual, are all dif- 
ferent from those of real ova. 
Another point of equal importance is these vivi- 
parous individuals of the Aphides have no proper 
ovaries and oviducts. Distinct organs of this kind 
I have never been able to make out. The germs, 
as we have before seen, are situated in mouiliform 
rows, like the successive joints of confervoid plants, 
and are not enclosed ina specirl tube. These rows 
of germs commence, each, from a single germ-mass 
which sprouts from the inner surface of the animal, 
and increases in length and the number of its com- 
ponent parts by the successive formation of new 
germs by the constriction process as already de- 
scribed. Moreover, these rows of germs which, at 
one period, closely resemble in general form, the 
ovaries of some true Insecta, are not continuous 
with any uterine or other female organ, and there 
fore do not at all communicate with the external 
world, on the other hand, they are simply attached 
to the inner surface of the animal, and their com- 
ponent germs are detached into the 
cavity as fast as they are developed, and thence 
escape outwards through a Porus genitalis. 
With these data, the question arises, what is the 
proper interpretation to be put upon these repro 
ductive phenomena we have just described? My 
answer would be that the whole constitutes only a 
rather anomalous form of gemmiparity ; as already 
shown, the viviparous Aphididae are sexless ; they 
are not females, for they have no female organs, 
they are simply g iparous, and the budding 18 
internal, instead of external as with the Polypi ant 
Acalephae ; moreover this budding takes on some of 
the morphological peculiarities of cviparity but these 
Waniaal 
