ON THE AGAMIC REPRODUCTION AND MORPHOLOGY OF APHIS 73 
simple segment; while those who admit a multiplicity of segments, 
appear to be misled by the position of the eyes and antenne, into 
regarding them as tergal appendages of the segments over whose 
sternal appendages they lie—as a kind of wings of the cephalic 
somites, in short. Again, it is supposed by many that the labrum 
and the lingua are the representatives of the appendages of distinct 
somites, a conception which is at once negatived by the study of 
their development. 
As I have endeavoured to show, there are certainly five, and 
hypothetically six, somites in the head of /vsccfa ; there are certainly 
at least three in the thorax; but the number in the abdomen has 
been as much disputed as the number in the head. Zaddach con- 
siders, as a general rule, ten to be the number of abdominal somites 
in Insect larvee; Westwood and Newport enumerate eleven in some 
Hymenoptera, and this last is, I believe, the maximum number of 
somites which has yet been found in the abdomen. Now, if we 
assume the number of somites in the head to be six, the number in 
the thorax three, and the number in the abdomen eleven, we shall 
arrive at twenty as the maximum number of somites in the body ot 
an Insect. 
This conclusion is in remarkably close accordance with the results 
obtained by M. Lacaze-Duthiers from his laborious and remarkable 
researches into the structure of the female genital apparatus of 
Insecta. MM. Duthiers finds that the vulva always opens between the 
eighth and ninth abdominal somites, and that in MNewroptera, in 
Orthoptera, in most Hemiptera, and in Thysanura, three somites inter- 
vene between the vulva and the anus, which is always placed at the 
very extremity of the body. There are thus eleven abdominal 
somites, and, therefore, a total number of twenty, in these four 
orders. 
Some Hemiptera have the last abdominal somite abortive, and this 
appears to me to be the case in Aphis. In Coleoptera and fynzenop- 
tera, the tenth and eleventh somites abort, nine only remaining: in 
Lepidoptera, finally, all three post-genital somites remain undeveloped. 
M. Lacaze-Duthiers’ researches tend to show that a fundamental 
unity prevails amidst those apparently most diverse apparatuses 
which we know as stings, borers, and ovipositors, and that they are 
always the result of a modification undergone by the ninth abdominal 
somite. 
I do not consider myself competent to give an opinion as to the 
details of the investigations to which I have just alluded, but 
I cannot refrain from expressing the belief that the labours of 
