200 Mr. B. T. Lowne on 
Cecidomyide unmistakeably approaches the phenomenon 
in Aphides ; the only difference is, that the germ cham- 
ber of the Cecidomyian larva becomes detached, and 
moves about in the cavity of the mother; whilst in 
Aphides, the germ chambers remain permanently attached 
by an apparatus, which in form and arrangement, repro- 
duces the conditions of the ordinary female organs.” 
In the agamic form of Aphides, we observe the same 
tendency to the non-development of the accessory sexual 
organs, in the absence of the spermathecz and collaterial 
glands. 
Lastly. With regard to the objection that the winged 
forms of insects are probably derived from the apterous 
or larval forms, [ am far from being sure that such is 
really the case. 
With respect to the Metabola, I think Gerstiicker, and 
others, have clearly shown that the larva is an acquired 
and not an original form. 
If further evidence be needed on this point, I think it 
is afforded by the relation borne by the larva of the 
Diptera to the embryo and perfect insect. As this rela- 
tion is highly remarkable, and as it is directly concerned 
in the conclusions I have arrived at on the relation of 
the larva of the Metabola and Ametabola, I will say a few 
words on the subject. 
The embryo of the blow-fly, twelve hours after impreg- 
nation, bears a closer resemblance to the pupa, than it 
does at any subsequent period of larval life. During the 
remaining twelve hours of embryonic life, a very remark- 
able change takes place; all those parts of the embryo 
which correspond with the head of the perfect fly, be- 
come converted into the imaginal discs of Weismann ; 
and do not again make their appearance externally until 
the pupa-state is assumed. This is quite analogous to 
the so-called hyper-metamorphosis of some Coleoptera: 
and especially reminds one of the manner of development 
in some Crustacea, where the embryo is surrounded, 
during development, by a kind of larval skin. 
The embryos of Ligia and other Isopods, with their 
larva-like skin, afford, to my mind, a clue to the origin of 
the metamorphosis of the Insecta. Suppose the embryos 
