DEVELOPMENT AND IMMATURE STAGES. 151 



them tlie very natural, but utterly erroneous deduction 

 that Hypopus was the male of Tyroglyphus. Had he 

 only known it Clarapede had disproved his own 

 theory in his own paper, for he really had found the 

 male over and over again but he did not recognise it as 

 belonging to the same species ; he made a new genus 

 for it and called it Rhizoglyphus Robini. Rhizoglyphus 

 is one of those exceptional creatures which have two 

 forms of male ; one with the third leg greatly enlarged 

 and the tarsus coming to a point, the whole joint being 

 claw-like but not provided with any real claw, this leg 

 being a clasping leg only ; the other with the third leg 

 an ordinary ambulacral leg, not differing from the other 

 legs and furnished with a claw. Both forms copulate 

 equally freely with the female, as I have ascertained 

 from personal observation, but they were at first sup- 

 posed to be different species until Canestrini established 

 their identity and the existence of intermediate forms. 

 Claparede recognised the form with the small third leg 

 as a male, but oddly enough mistook that with the 

 enlarged third leg for its female ; it never struck him 

 that either was the male of his Tyroglyphus Dujardinii. 



Claparede's suggestion that Hypopus was the male of 

 Tyroglyphus was, however, not only disproved by his 

 own researches, but it was disproved before he published 

 it had he known it ; but he was not aware that while 

 he was studying his species Professor C. Robin and 

 Dr. Fumouze were doing the same thing; they pub- 

 lished their paper* shortly before Claparede issued his. 

 They called the species Tyroglyphus echinopus, and their 

 specific name must stand, although Claparede's generic 

 one does ; therefore the species is now called Rhizo- 

 glyphus echinopus. Robin and Fumouze did not trace 

 the Hypopus, or apparently know anything about it ; 

 they did not breed it apparently, but they did recognise 

 and describe the male correctly. 



P. Megnin took up the subject of Hypopus in 1873, 



* " Observations sur nne nouvelle espece d'Acarien du genre 

 glyphe," in ' J. Anat. Physiol.,' 1868, t. v, p. 287, t. xx, xxi. 



Tyro- 



