AND DEVELOPMENT OF MELOE. 171 
envelope around the nucleus within an adult cell, and this is followed by the fissiparous 
division of the nucleus itself into two bodies, which, subsequently enlarging, have each 
their own proper cell-wall formed around them; after which the cell-wall of the parent 
structure disappears, and leaves the young nuclei free to be developed into separate cells, 
like that from which they have originated. Thus the end of the development of a forma- 
tive cell is the fissiparous division of its nucleus. This mode of development of the tegu- 
ment in the young animal, after it has left the egg, is confirmatory of the theory of 
Schwann with reference to that of the general tissues; and it also accords with the views 
of Kölliker respecting the division of the yelk cells in the ovum; and with original obser- 
vations made by myself, to be elsewhere demonstrated, on the mode of formation of the 
blastoderma. | 
If a transparent portion of the surface of one of the thoracic segments of a young Meloé 
which has been for some months in strong spirit, be covered with thin tale, with a little 
fluid around it, and be then examined by transmitted light with a magnifying power of 
four hundred and fifty diameters, we can immediately recognize the granular, nucleated 
external cells of the tegument. If then we approach the lens to the object, so as to be too 
near to have the external cells in focus of vision, the layer of cells beneath them is brought 
into view. The cells of this deeper-seated layer are smaller than those of the outer one. 
If the specimen examined has been several days from the egg, before immersion in spirit, 
then these cells, instead of having each a single granulated nucleus like those of the outer 
layer, are found to contain each two nuclei of equal sizes, closely approximated together, 
but perfectly distinct, and inclosed in one common envelope (fig. 8). In some of the cells 
the two nuclei are more separated than in others, while in those which have most 
recently changed they are closely approximated. Occasionally the original nucleus of a 
cell, not yet divided into two, is observed, in the commencement of its change, with a 
on on one surface; but this fact ean only be seen when the exami- 
fissiparous emarginati 
nation happens to be made on an insect in which the tegument has not far advanced in 
its changes. The fissiparous division of the nucleus thus appears to be the usual mode of 
growth of all cellzeform tissues. 
Although the solidified tegument supplies the place of a true skeleton in the Articulata, 
it is also the agent of other functions; which are of as much importance to the welfare of 
the animal physiologically, as this is anatomically. It is the medium of the transudation 
of effete matters from the surface of the body, the retention of which would be detrimental 
to the entire organism. The celleeform structure of the tegument enables us readily to 
understand its adaptation to this office. But, besides this, it is subservient to another 
function, which is equally important with that of transudation,—the aération or oxygena- - 
tion of the fluids. This is effected solely by the tegument in the very young embryo in the 
egg ; but as the embryo is advanced to maturity, the function is shared by, and, after birth, 
is almost entirely performed by respiratory organs, which originate in, and are constantly 
connected with the tegument as spiracles, or breathing orifices in the sides of the body 
(fig. 1 à b). i 
(fig ) among the last formed of the essential structures of the 
- These respiratory organs are ctore 
embryo. hard not been able to detect the existence of spiracles in Meloe until nearly 
