MORPHOLOGY. 
75 
within which the Aphides live, or the tangled masses of 
foliage often seen on the summits of various native 
annuals, like Silene inflata. 
Various devices are employed by Aphides to avoid 
notice. Some will actively run to the opposite side of 
a branch when danger approaches ; others will imme- 
diately drop to the ground if disturbed. Some have 
the curious habit of throwing up their hind legs when 
alarmed, which action gives a signal to the rest of the 
colony, which responds by doing the same act. Finally, 
some of this remarkable family appear to assimilate 
their colour very much to those of their food, and thus 
they escape observation. By rolling up leaves, and 
affecting their under surfaces, protection is gained 
from sun, rain, and winds, and doubtless then they 
are less open to the attacks of their many foes, winged 
and otherwise. 
The phenomena of reproducti?5n belong to the domain 
of physiology, but those of morphology and develop- 
ment belong to that department of natural science 
which treats of the gradual growth of the individual f 
and the processes connected therewith. Here, therefore, i 
a few remarks upon the latter subject can be best 
appended. 
THE MORPHOLO^JT OF APHIDES. 
The extreme rarity of the males of some living 
forms, such as those of the Bntomostraca, would seem 
to prove little more than that the influence of the male 
element ’ sometinies is exerted at a minimum. That 
the male in such cases is not wholly absent might 
even show how necessary is the conjunction of prim- 
ordial cells to perpetuate every species, though such 
a union may be deferred to very long periods. It may 
be pretty safely asserted that all Aphides originally 
proceed from impregnated ova, and at the end of their 
generations again they produce ova. We are in a 
