182 ZOOLOGY. 
give force to the idea of community of descent between these two 
classes, and community of structure in their exo-skeletons. But 2 
neither those who advocate 7 joints to the head, nor those who 
advocate 4, or 3, or 2, can claim that their particular views are : 
demonstrated ; and until they are demonstrated the advocates of 
the 1-jointed nature of the head have the advantage and will natu- 
rally relegate the other propositions to the limbo of pure theory. 
It is, moreover, difficult to conceive how those who include Arach- 
nids, and Myriopods under the term Insect can believe in any 
present community of structure between them. Si 
My own view of this matter is not badly-set forth in am CX 
cellent memoir by Dr. H. Schaum “On the Composition of the : 
Head, and on the Number of Abdominal Segments in Insects,” * f 
and to defend it properly would require a whole number of the - 
NATURALIST, and involve a discussion of the value of the specula- 
_ tions so freely indulged in on this head. For this I have neither 
time nor inclination, and a few words must suffice. I can see no. 
good reason why: the jointed appendages of the head should be 
made to represent separate head segments, any more than the 
non-jointed appendages; and if any good reason coul 
given, it ought to apply to the jointed legs of the thorax as — | 
well. Yet the apodous insect larva peveLors jointed legs as well- ne 
as the legged larva. To me the idea that the head is composed of, 
four joints is not a whit more tenable than the opinion that the 
thorax is composed of six. AS Schaum has well said, it is a ge 
eral law that an insect leaves the egg with the full complement of ; 
joints and none are ever added during metamorphosis. Yet many : 
larvee have a head without the slightest trace of a division into 3 
- subjoints, and such are frequently blind or even destitute of aP- 
tenne, though their'imagines possess both eyes and antennis i 
Now, how can these organs be said to represent, or: be developed 
from, joints which never had an existence? a d 
(2) I have the satisfaction of beihg in most excellent company 
from the days of Lyonet to those of some of our best modern 
_ authors, in considering an insect 13-jointed ; 
Tr 
Bees Ns Brie See RAUS SS 
EEFE U y aa See, TER NE E ae 
a E E A E or C = 
eae pes ee eo oe 
tion which the authoritative tone might be supposed to possess: 
My own experience fully corroborates the views of those authors 
-who consider that in no instance doe’ the number of joints, 
~ *Ann. and Mag. Nat. Hist; London, vol. xi, 3d ser., 1863, pp-173-19% 
Ee : 
os 
