HYFOFID^E. 245 



CASE It humbly appears to us that there must be some error here. 

 We render all justice to the painstaking truthfulness of M. 

 Dujardin and M. Megnin's observations. They are no doubt two 

 to one, but we must remember who the one is. Claparede was 

 one of the most distinguished physiologists, and most careful and 

 accurate microscopic observers of the present generation ; and as 

 Claparede's observations, now in the balance, lead to no incon- 

 gruous or unprecedented results, we own that we feel a preference 

 for them. If MM. Dujardin and Megnin are in error, its extent 

 would be the mistaking the containing mite for a Hypopus while 

 it was only a Tyroglyphus ; and the very considerable resemblance 

 that there is on a superficial view between the earlier stages of 

 Hypopus (so far as known) and Tyroglyphus, is the more sug- 

 gestive of the possibility of such a mistake. 



As regards the observations of Dujardin, he is either in error 

 in supposing that the contained mite was a Gamasus ; in which 

 case his authority as to identity of the containing mite is weakened, 

 or if he is right and M. Megnin right, then Hypopus forms not 

 only a stage in the development of Tyroglyphus, but also of 

 Gamasus. We must always remember that we are investigating 

 the development of an animal so minute, that it passes the portion 

 of its life now in question in the inside of a mite no larger than 

 its relative the cheese mite. 



As to M. Megnin again, his own account of his observation 

 contains one or two facts which seem to lend support to our 

 suggestion that, in its early stage, Hypopus is an internal insect 

 parasite. In his paper above mentioned he says, *'0n the 14th 

 of April, 1869, while preparing a Trombidium holosericeum for 

 anatomical study, we were much surprised to find, among the 

 red and branched hairs of this large Acarid, three Hypopi, in all 

 respects similar to that found on an ox by M. Deyrolle. In fine, 

 eight days later, having collected in a truss of old decaying hay a 

 great qu^^ntity of Gamasi and other Acarids, we found a female 

 Gamasus, to which adhered two Hypopi, in all respects similar to 



