HYPOPID^, 241 



CASE position, myriads of Tyroglyphi swarmed in his boxes ; when, on 



XIV' 



the contrary, the mushrooms on which they lived began to dry 

 up, his numerous Tyroglyphs disappeared in great part, and were 

 replaced by legions of a particular Hypopus, having all the 

 characters of Hypopus feroniarum of Dufour, or the H. dugesii 

 of Claparede. 



On renewing the provision of mushroom, which restored the 

 moisture, it was the Hypopi which disappeared in their turn, 

 replaced by myriads of Tyroglyphi. Twenty times the same 

 phenomenon was reproduced before his eyes. Persuaded that 

 these Hypopi must change their form in moulting, he had 

 isolated them at different times in small cages of glass, but with- 

 out success : they remained inert, sticking to the walls of the 

 cage, and as if deprived of life. The idea then occurred to him 

 to place them in contact with fresh mushrooms, and accordingly 

 he placed in their cages fragments of mushrooms completely 

 freed from eggs and animalcules. " In these new conditions," 

 says M. Megnin, " the Hypopi moulted and transformed them- 

 selves under our eyes into small octopod Tyroglyphi, not yet 

 adult. This fact shows," says he, " that the Hypopus is a transi- 

 tion stage of Tyroglyph ; but does the Hypoyus come from the 

 eggs, or is it the result of the transformation of hexapod larvae, or 

 of nymphs ?" and he gives the figure in the accompanying wood- 

 cut of the act of transformation which he saw. 



In pushing his researches further, he succeeded in finding an 

 inert octopod nymph, containing in its inside a Hypopus, ready 

 to change, in other words, he re-discovered what Claparede took 

 for the male. The result of his observations is thus stated : 

 " Here is what has been well shown. There are nymphs of 

 Tyroglyphus which transform themselves into Hypopus; and, 

 reciprocally, Hypopi which re-become nymphs of Tyroglyphi." 

 And the conclusion deduced from it is that "Hypopus is nothing 

 but a cuirassed adventive heteromorph, charged with the con- 

 servation of the dissemination of the species of Acarid which 



Q 



