218 J. MURRAY ON GASTROTRICHA. 



I have no better to offer, so I suggest that we leave classification 

 on broad lines till we know more, and classify in genera only. 



These have also been badly handled. Ehrenberg's two genera, 

 Ichthydium and Chaetonotus, will serve as a beginning of classi- 

 fication till we find something better. The distinction between 

 hairy and smooth is not important, and in many genera of 

 animals both types occur -e.g. Macrobiotus among Tardigrada, 

 but among Gastrotricha, if we are to have divisions at all, 

 we must be satisfied with very trivial characters. Miiller's 

 Cercaria poduva, which became the type of Ichthydium, was 

 probably a composite diagnosis, as some of his figures show 

 bristles. I have shown the unsatisfactory treatment of his genus 

 Lepidoderma by Zelinka, but, if his generic characters were 

 regarded in allotting species to it, it might serve as a temporary 

 artificial genus till we see our way out of the muddle. 



Ehrenberg's obsession for symmetry in classification led to 

 many obviously false associations of species, and tyrannised over 

 naturalists till a late period, even as late as 1864 affecting 

 Gosse. It is curious now to regard the genera once included 

 in the Gastrotricha Ptygura, Glenojihora and to think that 

 Sacculus and Taphrocampa were originally described by Gosse 

 as Gastrotrichs. 



Key to the Genera. 



A. Without a furca. 



1. Body with long bristles .... Dasydytes. 



2. Body without long bristles . Anacanthoderma. 



3. Head with antennae . Gossea (G. antennigera). 



B. Furca minute or obscure. 



4. Furca minute, large barbed bristles . Stylochaeta. 



5. Furca obscure, short ..... Setopus. 



6. Head with antennae . . . Gossea (two species). 



C. Furca conspicuous, body with bristles. 



7. Furca simple, bristles pointed . . Chaetonotus. 



8. Furca simple, bristles expanded at apex Aspidiophorus. 



9. Furca twice furcate ..... Chaetura. 



D. Furca conspicuous, body without bristles. 



10. Body with scaly armour . . . Lepidoderma. 



11. Body without scales .... Ichthydium. 



