170 INTERNAL ANATOMY OF INSECTS. 
1. It has already been observed that there are a few 
ovo-viviparous insects % the young of which exist in the 
ovaries at first as eggs, but are hatched within the body 
of the mother, and come forth in the living form of a 
larva and sometimes even of a pupa. Of the first de- 
scription are certain Diptera, the Aphides, and the Scor- 
pion. 
Reaumur has described two modes in which the lar- 
vae of the first are arranged in the matrix of the mother. 
In some they are heaped together without much ap- 
pearance of order, being placed merely parallel to each 
other b ; but in others they are arranged in a kind of ri- 
band — the length of the little animals, which are also 
parallel, forming its thickness — rolled up like the main- 
spring of a watch c . These larva? in general are not di- 
vided into two masses corresponding with the pair of 
ovaries in other insects, but form only a single one d . 
You must not suppose that these little fetuses lie naked 
in the womb of the mother ; each has its own envelope 
formed of the finest membrane, which, however, is not 
entirely divided from that of those adjoining to it, but 
appears to be one tube, which becomes extremely slen- 
der between each individual, so as when drawn out to 
look like a chain e . Reaumur seems to have thought 
that in these flies the larvae were never confined in any 
other case or egg f ; but De Geer sometimes found eggs 
in the body of Sarcophaga carnaria, though most gene- 
rally larvae, from which he conjectures that it is really 
ovo-viviparous, the eggs being hatched in the body of 
a Vol. III. p. 64—. " Plate XXII. Fig. 4. 
c Ibid. Fig. 3. * Reaum. iv. 414. 
' Ibid. t. xxviii./. 14, 15. f Ibid. 404. 
