OF GLTCIPHAOTS D0MESTICTJ8 AND G. SPINIPES. 



296 



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. 



CONCUEKENT INVESTIGATIONS BY M. MfiONlN. 



It appears that while I was engaged on these observations 

 M. Megnin was also investigating some points relative to the 

 GlycipJiagi, and, inter alia, almost the same subject as my own *. 

 We did not either of us know of the other being so occupied. 

 Meguin 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 Glyciphagus 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 

 Tyroglgphus into ^Uypopus is caused by unfavourable surround- 

 iiigs, states that under similar conditions he found that those of 

 GlycipJiagus 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 

 mass 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 bluwn 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. 



Meguin 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. 



