228 ROTIFER A 



Callidina revive after an exposure of 20 C. ( 4 F. or 36 of 

 frost), and immersion in hot water at 70 C. (158 F.). They will 

 also resist deprivation of air in a vacuum of an ordinary air-pump, 

 but not the all but perfect exhaustion of the Sprengel pump. 



A very curious fact in relation to this Class is that often 

 when a new form is once described from a single locality, fresh 

 and widely distant stations for it rapidly become known. 1 Thus 

 Pedalion mirum, first found at Clifton in 1872 by Hudson, was 

 a few years after captured in a small pool above tide-marks on a 

 rocky islet in Torres Straits. Since then it has been recorded 

 from many different European stations, and a second closely allied 

 species has been found in Finland. So a species of Ehrenberg's 2 

 was not seen again till within the last decade or so ; but since 

 then it has been independently found and described by six 

 observers, who have given it as many distinct generic names. 

 In the case of Pedcdion it may well be that, as Hudson suggests, 

 the species is of southern origin and has followed the flag, the 

 winter egg being conveyed in dust by ships or travellers. 



The above account of the habits gives the key to the collec- 

 tion of the various forms. The weed-loving species are collected 

 with the weeds, and will keep with these in vessels if screened 

 from direct sunlight and protected against dust. The free- 

 swimming forms may be collected by sweeping with a net of 

 fine gauze, with a bottle fixed in the bottom. 



Except for their power of resisting desiccation, Eotifera are 

 not very long-lived, and the males are especially short-lived ; the 

 most exact observations are those of Maupas on Hydatina. He 

 found that the greatest age of the unfertilised female was 

 thirteen days, during which it could produce some fifty eggs ; the 

 fertilised female lives for seven or eight days, producing about 

 sixteen eggs ; while the male dies in two or three days. 



The preservation of Eotifers has been recently reduced to a 

 fine art by Kousselet, who uses a solution consisting of cocaine 

 hydrochlorate, 1 gramme; water, 50 cc. ; and methylated spirit, 

 12 cc. This will keep without deterioration. When in use it 



1 See Dr. Hudson's very suggestive presidential addresses to the Royal Micro- 

 scopical Society, published in their Journal, vols. ix.-xi. 1889-91. 



2 Euchlanis lyiiceus.This is clearly not an Euchlanis, and of the six names 

 referred to Plocsoma, Gomphogastcr, Gastropus, Gastroschiza, Bipalpus, and 

 Dictyoderma the first has priority, and the other five drop by the laws of zoolo- 

 gical nomenclature. 



