92 BRITISH TYROGLYPHIM:. 



them to be dermal processes ; he says * that they are 

 raised on small elevations on the floor of the pocket, 

 and that they are conical. He says also that the large 

 base, by which expression he apparently means the 

 distal end, serves as a sucking-disc ; and that the wall 

 of the cone is a chitinized membrane, while the disc is 

 thinner and flexible ; if the sucker be much projected 

 the disc becomes domed ; but this form is opposed by 

 the retractor muscle, which makes it plate-like. The 

 projection of the sucker is said to be effected by the 

 flow of blood into it, and its action as a sucker by a 

 simple but powerful retractor muscle within the sucker, 

 and inserted into the proximal side of the disc and 

 which passes transversely across the body to the 

 epimeron of the fourth leg. The withdrawal of the 

 whole sucker is said to be due to a muscle-bundle 

 attached to the edge of the disc. Nalepa is convinced 

 that it is a true sucker and functions as such. I do 

 not however gather from his paper that he has seen 

 the sucker in action ; indeed, it would be hardly pos- 

 sible to do so in consequence of the position ; he 

 apparently judges from the anatomical structure which 

 he describes. 



Claparedef and Nicolet,J both writing of the Oriba- 

 tidge, and Fumouze and Robin, writing of the Tyro- 

 glyphidae, also considered that the organs were true 

 suckers. On the other hand, Megnin,|| also speaking 

 of the Tyroglyphidae, entirely denies that the organs 

 are suckers ; he says that in the male they serve to 

 separate the male from the female after the coitus ; and 

 that in the female they have not any function connected 

 with coition, but serve to guide the egg during oviposi- 



* Abtheil. I,' pp. 211213. 



f " Studien an Acariden," in ' Zeit. wiss. Zool.,' 1868, Bd. xviii, 

 p. 511. 



J " Histoire naturelle des Acariens qui se trouvent aux environs 

 de Paris," in 'Arch. Mus. Paris,' 1855, t. vii, p. 415. 



' Mem. Acar.,' pp. 591, 592. 



|| " Memoire sur les Hypopes," in ' J. Anat. physiol.,' 1874, pp. 239, 



