216 the president's address. 



curious to see what different views acarologists have held as to the 

 nature of these animals. All the earlier writers considered them 

 to be distinct organisms, and gave them generic and specific 

 names. Dujardin first suspected that they were only forms of 

 gome other known creatures; he found them abundant with and 

 on Gamasidce, and expressed his conviction that Hypopus was a 

 young Gamasus. Gerlach was probably deceived by the hind legs 

 and the parasitism, and declared them to be adult itch-mites. 

 Gervais, without giving any reason, classes them as adults of the 

 genus Tyroglyplms; this is somewhat strange, because they do 

 not look in the least like Tyroglyphus. Gervais does not profess 

 to have made any discovery, and yet it is the first instance in which 

 the connection, which really exists, between Tyroglyphvs and 

 Hypopus, is referred to. Claparede followed this idea up. He 

 was not a man to put forward anything without reasons ; he had 

 previously been studying Hoplophora, one of the Qribatidce. In 

 this creature the nymph is soft and white, the adult hard and 

 chitinous. Claparede now took to rearing one species of Tyro- 

 glyphus. He got plenty of larvae and nymphs, plenty of adult 

 females, but no adult males ; but he did get a number of hard, 

 chitinous Hypopi, and he satisfied himself that each of these 

 emerged from a soft white Tyroglyphus-nymiph, leaving only a cast 

 skin behind it. What could be more convincing ? Claparede 

 announced his discovery that Hypopus was the male of Tyro- 

 glyphus. Unfortunately this was disproved even before it was pub- 

 lished. Robin and Fumose happened to be studying the same 

 Tyroglyplms at the same time ; the Swiss and the French 

 naturalists were working in entire ignorance of one another's 

 labours. Robin and Fumose published their results a few days 

 first ; they had found and bred the male in abundance, but it had 

 not struck them that the Hypopus belonged to the same life- 

 history. Next came Megnin, who, as the result of experiments in 

 which he alternately allowed his breeding boxes to get dry and 

 then supplied fresh pieces of fungus, came to the conclusion that 

 Tyroglyphus-nym])h.s had the power of changing into Hypopi when 

 drought or other circumstances were unfavourable to their exis- 

 tence as Tyroglyphi, and of changing back again when circum- 

 stances were once more propitious. Afterwards Andrew Murray 

 brought forward the somewhat startling theory that Hypopus was 

 a ferocious internal parasite, which entirely eat up its host, the 



