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MYRIAPODA. 
The structure of the duct and of its numerous 
ovisacs is best seen in those specimens that 
have not yet arrived at maturity, or in those 
which have just deposited one laying of eggs. 
In these individuals the oviduct, to within a 
short distance of its division into two outlets, 
is studded with minute ovisacs, each filled with 
the rudiments of its minute ovum. Its ge- 
heral appearance in a female, that has recently 
deposited its eggs, is completely botruoidal, 
very like the ovary of Birds, some ova being 
always fully developed, and ready to pass into 
the oviduct, while others are in various stages 
of developement, many of which are imper- 
oe except with the aid of a powerful 
ens. 
But the most remarkable condition of the 
female organs in the Julide is their double 
vaginal outlet, as in Crustacea, although the 
oviduct itself is a single tube until near its 
termination, where it is divided into two short 
canals, which from a slight opacity at their 
base, where they join the single duct, appear, 
when seen by transmitted light, to be separated 
from it by a valve or duplicature of the lining 
mucous membrane. The vaginal orifices are 
simply two nipple-shaped portions of the tegu- 
ment, with somewhat oval apertures sur- 
rounded by a corneous ring, from which is 
developed a circle of minute hairs. They are 
Situated on the under surface of the fourth 
segment of the body, and correspond in posi- 
tion to the insertion of the legs in the third 
segment. 
Ova.—We have already seen from Mr. New- 
port’s description of the female generative 
system of Julus, that the ova are formed in 
Separate ovisacs, from which they issue com- 
pletely constituted eggs, into the cavity of the 
ovarium or common duct, through which they 
are expelled from the body after impregnation ; 
and we now proceed to lay before the reader 
the important results of the investigations of that 
distinguished anatomist relative to the struc- 
ture of the ova themselves, and the progress 
of embryonic developement. The existence 
of the ovisacs in Julus as single isolated cap- 
Sules on the exterior of the oviduct, in each 
of which a single egg is produced, is, Mr. 
Newport observes, a circumstance particularly 
favourable to a minute examination of the 
©vum in all its states, especially as ova are 
found at the same time in every stage of de- 
velopement. The smallest ovisacs appeared 
like very minute glandiform bodies, developed, 
as it were, immediately from the structure of 
the duct itself, and in these the rudiments of 
the future egg had already begun to be pro- 
duced. The smallest rudiments of eggs ex- 
amined were of an elongated shape, and as yet 
not more than three, or at most four blood- 
globules in diameter. They appeared already 
to have distinct parietes, and to be filled with 
very minute graniform cells of a uniform size, 
slightly opaque, and of a yellow colour. The 
diameter of these cells, as nearly as could be 
ascertained by direct comparison, was equal to 
about one-third of that of a blood-globule. 
In the midst of these cells there was a larger 
but much more delicate structure of a circular 
553 
form and equal in size to about two of the cells, 
but whether this was the germinal vesicle or its 
macula could not be determined. Other ovi- 
sacs twice the size of the foregoing were filled 
with similar contents, and from the opacity 
and yellow colour of the graniform cells, it 
was evident that they constituted the yelk in 
one of its earliest stages. At a later period 
both the yelk and its including vesicle are in- 
closed in a distinct membrane—the membrana 
vitelli, and before its escape into the oviduct 
all the parts of a perfect egg, namely, the yelk, 
the germinal vesicle with its macula, the mem- 
brana vitelli, the albumen, and likewise the 
shell lined by the membrana externa or chorion, 
are completely formed. 
Evolution of the embryo—The develope- 
ment of the young Julus Mr. Newport di- 
vides into several distinct and well-marked pe- 
riods, during each of which phenomena are pre- 
sented of the utmost interest, both to the phy- 
siologist and in an entomological point of view. 
The first period extends from the deposition 
of the ezg to the gradual bursting of the shell, 
and exposure of the embryo within it, occu- 
pying the space of twenty-five entire days, 
during which the egg acquires a sensible in- 
crease of bulk. 
On the nineteenth day there was a complete 
alteration in its form; it was more obtuse at 
both ends, and had become much larger, and 
the outline of the embryo, coiled up within the 
shell and nearly filling the whole interior, was 
very distinct, although, as yet, there were no 
rudiments of limbs or even of a division of 
the body into distinct segments. On the fol- 
lowing day, the twentieth, the outline of the 
embryo was more apparent, and on its concave 
or ventral surface there were faint traces of a di- 
vision of the body into six segments (fig. 31 reel 
Fig. 317. 
Up to this period Mr. Newport 
was unable to detect any funis 
or umbilical cord attached to 
the embryo, although, in conse- 
quence of Rathke’s observations 
in Crustacea, such a structure 
was particularly sought for, the 
whole body still appearing to be 
formed of cells of different sizes. 
From this time the egg be- 
came every day larger until the twenty-fifth 
day, when it was greatly distended and began 
to assume a kidney-shaped appearance, and 
commenced bursting longitudinally in the me- 
dian line of the dorsal surface, the back of 
the soft and perfectly white embryo gradually 
pressing through the opening. 
In the second period of developement the 
embryo is exposed to a new medium, and 
perhaps derives the means of its further growth 
from external sources, although it is still enve- 
loped in the foetal membranes and retains its 
connection with the shell. 
The liberation of the embryo is a remarkably 
slow process as compared with the escape of 
other animals from the egg. In Mr. New- 
port’s observations, from ten to twelve hours 
* This and the succeeding figures are copicd 
from Mr. Newport’s paper, before quoted. The 
objects have been magnified twenty-five diameters. 
