344 Miscellaneous. 
sac. This sac is soon formed, and the ova are deposited in its 
interior. The embryos are rapidly developed, and their escape from 
the ‘sac appears to cause the death of the female; at least, Mr. 
Agassiz has never met with females after their embryos have escaped. 
The embryos at the moment of issuing from the sac have a triangular 
outline, their body diminishing rapidly towards the posterior ex- 
tremity. The development of these embryos presents an example of 
the most simple evolution observed among the Polychetic Anne- 
lides.—Journ. Bost. Soc. Nat. Hist. viii. p. 392. 
Note on the Reproduction of the Larve of Insects. 
By Professor Nicotas WaaGner, of Kasan. 
Professor N. Wagner has discovered a fact in the natural history 
of insects which at first sight appears incredible; but, as it is sup- 
ported by preparations, the inspection of which by Prof. de Filippi 
completely convinced him of the truth of Prof. Wagner’s observa- 
tions, a short notice of the singular results arrived at by the latter 
cannot but be acceptable to our readers. 
In June 1861 Prof. Wagner found, under the bark of a dead elm 
in the vicinity of Kasan, some whitish apodal worms, the organization 
of which proved them to be larvee of insects. Each of these larvee 
was filled with smaller larvee. This was nothing remarkable, as cases 
of parasitism are well known to be exceedingly frequent among in- 
sects. But Prof. Wagner was justly struck by the fact that the in- 
cluded larvze were perfectly identical, even to the smallest details, with 
the enveloping larvee. By this identity he was led to assume that 
the included larvee represented a second generation produced by the 
enveloping larvae. This would therefore be a case of alternation of 
generations even more surprising than that of the Aphides. Pe 
Improbable as this interpretation may appear at the first glance, it 
has several circumstances in its favour. Amongst these the principal 
are the following :-— 
1. It seems impossible to assume that a parasitic larva can pre- 
sent an organization perfectly identical with that of the organism 
which nourishes it. 
2. The parasites which deposit their eggs in a single insect, de- 
posit the whole at once, and these eggs are simultaneously developed. 
But Prof. Wagner found in one and the same enveloping larva in- 
cluded larvee presenting the most various phases of development. 
3. Parasitism is an accidental phenomenon, whilst all the larvee 
observed presented included larve at a certain degree of development. 
4. The size of the eggs of a given species is constant, whilst the 
reproductive bodies which here play the part of eggs exhibit very 
considerable variations of size. 
5. In the interior of the larva of the second generation a third 
generation is produced, precisely similar to the first two. 
Professor. Wagner has observed three other species of the same 
genus, all presenting this singular mode of reproduction. The per- 
fect insects are still unknown. From the appearance of the larve, 
they seem to belong to the order Diptera.—Siebold und Kolliker’s 
Zeitschrift, 1863, p. 544. ; 
