12 THOMAS HENRY HUXLEY 



Protozoa, with which the sponges were then associated. 

 One of Huxley's aims was to reduce the Radiata to order, 

 breaking it up into smaller natural groups, and determin- 

 ing their affinities so far as possible. 



His papers on Medusae had succeeded in doing this 

 for one large set of forms, and the paper now under 

 discussion was not merely a description of a new animal, 

 but also a successful attempt to define and delimit the 

 Protozoa. Huxley's view, now (if sponges are ex- 

 cluded) universally accepted, that these are of relatively 

 simple structure, directly traversed the authority of the 

 celebrated Ehrenberg, already challenged by a number 

 of distinguished naturalists. 



2. " On the Anatomy of the Genus Tethya" (a sponge). 



3. " On the Auditory Organs in the Crustacea." 



The much-vexed question as to the position of these 

 structures (to which another function is now ascribed) 

 in the higher Crustacea, such as prawns and the like, is 

 definitely settled in this paper. 



4. " Observations sur la Circulation du Sang chez les 

 MoUusques, des Genres Firole et Atlante " (Ann. des 

 Sci. Nat., XIV, 1850, pp. 193-5. Sci. Mem., i, vi, p. 36). 

 — Here we have a positive contribution to the physiology 

 of certain pelagic snails, founded upon observations made 

 on living specimens. Even at the present day physio- 

 logical work on invertebrates is relatively scanty, and 

 that so young a naturalist as Huxley then was should 

 devote some time to it is one of many proofs of the wide 

 nature of his interests. 



5. " Observations on the Genus Sagitta" (Brit. Assoc. 

 Rep., 1851. Sci. Mem., i, x, p. 96). — The little arrow- 

 worms (Sagitta, etc.) occur in vast numbers in the float- 

 ing population (plankton) of the sea, and their classifi- 

 catory position is still a moot point. In this short paper 



