OF GLYCIPHAGUS DOMESTICUS AND G. SP1NIPES. 
295 
from the nymphs, so that there could not be any doubt of the 
species, or of the process being a regular one. 
I also in January 1888, and again in April of the same year, 
dissected numerous reticulated cases from which the nymph had 
emerged ; in almost every instance I found within the case an 
unmistakable cast Hypopial skin having perfectly distinct legs. 
Concurrent investigations by M. M£gnin. 
It appears that while I was engaged on these observations 
M. Megnin was also investigating some points relative to the 
Glyciphagi , and, inter alia, almost the same subject as my own *. 
We did not either of us know of the other being so occupied. 
Megnin approached the matter from a standpoint different from 
mine : he did not find an object which excited his curiosity to 
discover its cause ; but it struck him that as Tyroglyphus has 
a Hypopial stage, so closely allied a genus as G-lyciphagus ought 
also to have it, and he deliberately set himself to search for 
that stage ; but he tells us that he searched in vain ; he tells us, 
however, that he discovered an equally curious phenomenon, which 
he says shows how prodigal nature is in processes for preserving the 
lower creatures. He, believing that the change of a nymph of 
Tyroglyphus into a Hypopus is caused by unfavourable surround- 
ings, states that under similar conditions he found that those of 
Glyciphagus became inert, that a liqueficationof all the organs took 
place “ as in a change of skin,” and that the gelatinous substance 
collects in the cavity of the “ thorax ” in the form of a spherical 
m-iss surrounded by a chitinous envelope and thus forming a cyst 
very similar to those formed by some Infusoria previous to the 
drying up of the water in which they are contained. Megnin 
suggests that in this condition the dried nymphal skins containing 
the cysts would be blown about by the wind and would thus 
finally arrive at some place where the conditions would be favour- 
able and would then emerge, and that the species would be thus 
distributed. 
Megnin says that his species were G. spinipes and G. cursor , 
which latter is, as before stated, presumably the same as G. domes- 
ticus ; but he does not distinguish between the life-histories of the 
two, nor identify any particular observations with either species. 
I do not intend here to discuss the vexed question of whether 
the liquefication of the organs of an Acarus during ecdysis is 
* Comptes Rendus, ciii. (1886) pp. 1276-8. 
