180 BRITISH TYROGLYPHID^E. 



the margin of the vagina, which has already assumed 

 the form of the sexual external opening. 



As Nalepa's account abstracted above did not seem 

 to me perfectly clear on the point, I have carefully 

 observed to see whether the nymph from which the 

 adult emerged showed any sign of external sexual 

 organs ; I made my observations upon Histiogaster 

 entomophagws, Garpoglyphus anonymus, and Tyroglyphus 

 siro ; in each case the creature was isolated in a cell 

 alone so as to avoid any possible mistake; numerous 

 specimens were observed, especially of H. entomophagus, 

 which I found the most favourable species ; but in no 

 instance did the nymph show external sexual organs, 

 although the internal organs might sometimes be more 

 or less seen through the skin. During the later stages 

 of ecdysis the organs of the adult may possibly be 

 seen a little through the nymphal skin. 



THE EODYSES. 



Numerous authors have dealt, more or less, with the 

 changes of skin of the Acarina in general, and of 

 that of special families ; I do not, however, think that 

 it will be necessary here to go in any way exhaustively 

 into the literature of this subject ; it will be sufficient 

 if I refer briefly to the principal controversy which has 

 arisen between acarologists upon the subject, and then 

 give a condensed account of the best observation 

 which has been made upon the ecdyses of the Tyro- 

 glyphidao. 



Gudden,* writing concerning the parasitic Sar- 

 coptidse, stated that at the ecdyses the whole of the 

 inner parts of the creature return to an amorphous 

 mass, like the egg ; and that from this the new creature 

 was formed, as from an egg. 



Megninf fully supported this view, and extended it 



* " Beitrag zu den durch Parasiten bedingten Hautkrankheiten," 

 in ' Arch. f. phys. Heilk./ Stuttgart, 1885, p. 28. 



f 'Les parasites et les maladies parasitaires,' Paris, 1880, p. 214, 

 and numerous other writings. 



