318 Miscellaneous. 
under the name of Anoetus, an Acarus found by Dr. Manceau de Cha- 
labre upon the wing of a bee, has been led to extend his researches 
to several allied species, and he has recognized that they ought to be 
united with Hypopus ; 7. e. that they, like his Anoetus, have neither 
a mouth nor a digestive apparatus ; also that they are provided with 
suckers upon the posterior part of the abdomen, and that these 
suckers merely serve to fix them at their will, in readiness for their 
last metamorphosis, which is effected at the expense of the internal 
nutritive matter which they have received at their birth. 
In 1847, M. Dujardin first found, upon Musca stabulans of Fallen, 
a Hypopus in the same state as the Acarus muscarum of Degeer, and 
it was in the case of this dearus, which was ;%5ths of a millimetre in 
length, that he was enabled to determine the absence of the mouth 
and intestine. Since then, he has found other species upon Séa- 
phylini and Cryptops, but having the same organization; lastly, in 
September 1849, he found some upon a fern, Ceterach officinarum, 
among which there were a certain number of shells or teguments ; 
these were perfect, but empty, transparent, narrower, and consequently 
more like those which he had seen upon the wing of the bee: the 
greater number were living, and continued to live in water; and the 
power with which these dcari are able to fix themselves to a plate of 
glass was then noticed. Some of them, which were few in number, 
and had become immoveable, exhibited through their tegument 
another form of Acarus which filled the whole of its internal cavity, 
and which were furnished with a mouth, having at the same time 
palpi and chelicera like the Gamasi and the Dermanyssi which live 
in great numbers in the same situation. From that time it became 
evident that the Hypopi, which had no mouth, nor any possible 
mode of growth, and which lived fixed upon polished surfaces that 
could yield them nothing —it was evident, shall we say, that these 
Hypopi are the larvee, or rather, if we may use the expression, the 
ova furnished with feet, in the interior of which, without any food 
derived from without, the young Gamasus is formed, solely at the 
expense of the contained substance. 
Consequently, M. Dujardin has been enabled to search for and find 
other Hypopi upon all the insects infested by the Gamasi, such as 
the Geotrupide, the Necrophoride, the Humble-bees, &c. They are 
most commonly found at the base of the abdomen, or beneath the 
first rings, or in the anfractuosities of the metathorax ; but judging 
from the diversity of their forms, we should think that there would 
be different species of Gamasi, or Dermanyssi, or even Uropodi. Other 
species have been found by beating the branches of trees ; and lastly, 
one species, which is very remarkable by its method of fixation, has 
been found upon subterranean rodents (drvicola subterranea), upon 
which also the Gamasi are parasitic. The latter Zypopus, in fact, 
would not have been able to fix itself upon the hairs or upon the skin 
by the suckers ; hence it is furnished, beneath the upper part, with a 
pair of striated lobes or tubercles, which becoming approximated like 
two lips, firmly embrace the single hairs of the mammifer. 
In short, the Hypopi are Acari with eight feet, without either 
mouth or intestine, and which, being deprived of all means of alimen- 
