DEVELOPMENT AND IMMATURE STAGES. 149 



quantities of Hypopi on Musca stabulans, on beetles, on 

 bees, on Geterach officinarum, etc. ; he watched them 

 carefully and intelligently ; he observed the absence 

 of mouth-organs, and as he considered of any mouth 

 at all, and of any reproductive organs. He also 

 noticed that some Hypopi immediately before the 

 ecdysis contained within their skin, and completely 

 filling it, an Acarus entirely different from themselves ; 

 this inner creature possessed chelate mandibles and 

 palpi ; he stated Gamasids were Acari ; they had chelate 

 mandibles and palpi similar to those seen within the 

 Hypopus ; they were to be found on flies, on beetles, 

 on bees, and in other places where he found Hypopi ; 

 Dujardin usually found the two together ; the infer- 

 ence to be drawn from these facts appeared obvious ; 

 Dujardin announced that Hi/popus was the young of 

 Gamasus ; it never struck him that Gamasus might be 

 a predatory creature which devoured the soft-bodied 

 Acari which emerged from the hypopial skin. We 

 know now that Dujardin was in error, and that there 

 is not any connection between Gamasus and Hypopus ; 

 but with the exception of Duges' query above referred 

 to, Dujardin was the first person who suspected, and 

 quite the first person who proved, that Hypopus was 

 an immature form of some Acarus totally different in 

 appearance from itself. 



Fiirstenberg in 1861 * in his great work on the 

 Sarcoptidse of mammals figured and described an 

 Acarus which he considered as belonging to Koch's 

 genus Homopus, and which Grwilt had found in 

 immense numbers on the skin of a recently stuffed 

 elephant ; for which, not very sufficient, reason he 

 called it Homopus elephantis. It is not quite clear 

 why Fiirstenberg included it in his book at all, as he 

 expressly says that although a parasite it is not an 

 itch-mite ; possibly it was because Gerlach held a 

 different opinion, and called it Symbiotes elephantis, 

 but having included it Fiirstenberg gave a very 



* ' Der Kratzmilben der Menschen uud Thiere,' Leipzig, 1861, p. 222. 



