SWAINSON. 573 



remember, proceeding in the contrary direction, considered 

 the Tunicata to be a very distant tribe, from which the Mol- 

 lusca could trace back only a doubtful descent ; and Blain- 

 ville made of the Tunicata and one or two other small tribes, 

 a sort of border clans, with which he tenanted a space, other- 

 wise waste, that lay between the Mollusca and the worms. 

 Mr. Macleay's decision as to the rightful position of the orders 

 of the Mollusca, and their catenation, was more ingenious ; 

 and in accordance with his general theory, that the series 

 of organic creations form, in their progress, a series of circles, 

 " rolling wheel within wheel, ad infinitum" Every circle 

 was a separate class, with its members forming an intimately 

 associated community, yet intimately connected with all the 

 adjacent and even the furthest remote circles, either by ties 

 of organic affinity or of analogy ; the ties of affinity proving 

 the immediate connection of the circles and their proper 

 position in the one that embraced the whole ; the analogy 

 declaring itself in certain common peculiarities of form and 

 habits which proved how the corresponding groups of sepa- 

 rate and even distant circles, were made to symbolise each 

 other. Every circle, moreover, was presumed to be formed 

 of five other circles, each of which was resolvable into five 

 lesser ones, and still even then revolving with a narrower and 

 narrower range as they successively descended to embrace in 

 the circling vortex, the lower and the lowest entities of crea- 

 tion. Thus the animal kingdom was supposed to form a 

 circle that included five great circles, one containing the 

 Acrita or Polypes, and infusory animalcules ; the second the 

 radiated ; the third the annulose ; the fourth the vertebrated ; 

 and the fifth the molluscous animals, which, in their most 

 degraded forms, return to and merge into the circles of 

 Acrita. The circle of the Mollusca should, of course, have 

 five classes ; but Mr. Macleay's attention not having been 

 particularly directed to this tribe, he could only determine 

 certainly the Acephala and the Pteropoda as occupants of 

 it, and the Brachiopoda doubtfully ; while the Cephalopoda 

 and the Tunicata were deemed to be osculant groups, the 

 former allying the Mollusca with the Vertebrata, and the 

 latter making a similar alliance with the Acrita.* 



Mr. Swainson, an able and zealous disciple of Macleay's, 

 first attempted the application of this theory, but in a m odi- 

 fied form, to the classification of the Mollusca in 1835,-)* and 

 more fully in 1840. J Of the groups which constitute every 



* Kirby and Spence's Introd. to Entomology, iii. 12 ; and iv. 359. 

 *t* Elements of Modern Conch ology. Lond. 1835. Duod. 

 J Malacology ; or, Shells and Shell-fish. Lond. 1840. Duod. 



