446 TRANSFORMATIONS OF INSECTS. 
The editors of the American Natural History Miscellany, 1860, 
state that the six-footed young one has enormous legs, and that 
the head is separated from the hind body. The young tick has 
terrible jaws, with which it buries its head and fore-part of the 
body within the tissues of the deer. The perfect tick has eight 
legs, which are short, and a large body. 
When considering the strong structural relation between the 
spiders and true insects, the history of the development of the first 
mentioned creatures within the egg and that of the metamorphoses 
of the tracheary order should never be forgotten. The early con- 
dition of the spider within the egg has a strong resemblance to 
that of the insect, for the head is not then forced into the chest, 
and there are traces of segments on the body; moreover, the six- 
legged condition of the water mites and some ticks in their larva 
condition refers back, like the other facts, to a common ancestry 
with the Zzsecta. 
The water mites, although they rarely care to quit the depths 
of the streams and ponds, do so at their pleasure, and run over 
the surface, and it is evident that they are not so perfectly 
adapted for aquatic life as many insects. Their trachee are 
not arranged as branchiz, and this consideration, amongst many 
others, leads to the belief that their present mode of life was not 
original. In a note to the admirable article by Audouin in the 
“Encyclopedia of Anatomy and Physiology,” Dr. Todd writes :— 
“ Mr. Blackwell has related an accidental discovery of the power 
of some spiders to abstract respirable air from water. Several 
individuals have preserved an active state of existence under 
water for six, fourteen, or twenty-eight days, spinning their lines 
and exercising their functions as if in air, while others have not 
survived a single hour.” 
The case of the water spider, Avgyroneta aquatica, whose diving- 
bell shaped nests under water, and whose method of carrying down 
air to fill them with, are so well known and so constantly referred 
to in all the books on natural history, loses much of its strangeness 
-and uniqueness when the above-mentioned facts are considered. 
It does not undergo a metamorphosis, however, so that there is no 
necessary connection between an amphibious Arachnidan existence 
and a sequence of the larval, nymph, and adult condition. 
