ARACIINIDA ACARl. 
2G9 
two, rarely more ; but in one dilated sac, containing many hairs, a com- 
pany of thirteen individuals was discovered. The examinations were 
mostly confined to the skin of the nose (Simon), and the external organ 
of hearing (Henle, Miescher). Simon observed three different states of 
the animal, which in many points varies remarkably from other Acari, 
principally in the legs, which are short stumps like those of the Tardi- 
grades, furnished at the end wdth claws. In the most frequent form the 
bod}^ is long and narrow, linear, the abdomen much elongated, and there 
are four pair of legs. The parts of the mouth are composed of a rather 
short, prominent proboscis, which is formed by an under-lip resembling 
a myrtle -leaf, and pointed mandibles lying upon it, and a pair of two- 
jointed palpi, the little knob-shaped terminal joint of which is moveable 
in all directions. In other forms the tarsi are the same ; but the abdo- 
men is remarkably shortened and conical. A third form has the long 
but still slenderer form of body of the first, but only three pairs of legs. 
This last I consider as the youngest condition, the second the more 
advanced. It does not appear to me probable, that the development is 
concluded in these three forms, and further observation is required. 
The internal structure is as yet unknown, as also the organs of propa- 
gation. So long as this is the case, it remains doubtful whether all these 
forms may not be young states of an Acarus, perhaps of a quite different 
shape, and found in other places. With this impression, Simon has not 
given it a generic name, but only marked it as Acarus folliculorum. 
Miescher was not satisfied with this name, and has called it Macrog aster 
platypus. 
Another Acarus has been found four times in comedones of the 
human skin, by Prof. Erdl, and is figured in Jul. Vogel leones Histologim 
Pathologicse, t. 21, f. 7. It is not accurately defined ; but the figure points 
to a Dermanyssxis, almost exactly agreeing with the D. avium, even to 
the longer proboscis, which considerably projects beyond the palpi. 
For some time there was much noise in England about an experi- 
ment by Crosse, who obtained, by galvanism, a peculiar species of 
Acarus. The matter was brought before the Entomological Society of 
London last year. Newport made a communication from a Mr. Wheekes, 
who had obtained Acari in the same way as Crosse. Gray, on the other 
hand, stated, that Children has also instituted a series of experiments 
at the British Museum, precisely similar to those of Crosse, without ob- 
taining a single Acartis (Proc. Ent. Soc. p. 55 ; Ann. Nat. Hist. x. p. 69). 
It was afterw'ards mentioned in the Entomologist (p. 307), that an Ento- 
mologist in Exeter (not named) had proved the Acarus of Crosse to be a 
well-kno\vn species widely distributed in houses, and added, that Crosse 
had a whole nest of them in his house, without being aware of it ; and 
so it happened, that if one of them accidentally got into his apparatus, 
he believed that he had obtained it by his experiment. 
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