268 On the Classification of Animals 



and if of a multiplicate, tliey are Worms. The very small num- 

 ber of segments present, when any are distinct, the character of 

 the dentate mandibles (for mandibles are not found in the inferior 

 subdivisions of Worms), and the resemblance in the form of some 

 species to Daphniee and other Entomostracans, sustain the view- 

 that they a,re Crustacean. 



The Cirripeds appear to be only attached, amplificate Ostra- 

 coids. (See pages 84, 85.) 



The subdivisions of the orders of Insecteans and Crustaceans 

 are then the followino^ : — 



Insects. 



Spiders. 



Myriapods. 



Decapods. 



Tetradecaps. 



Entomostr. 



ft. Prostheuics or 

 Ctenopters. 



y. Metasthenics or 

 Elytropters. 



a. D. Apters. 



b. D. 



Araneoids. 



Scorpionoids 

 Acaroids. 



Chilopods. 

 Diplopods. 



Brachyurans. 



Macrurans. 

 Gastrurans. 



Isopods. 



Amphipods. 

 Trilobites, ? 



Carcinoids. 



Ostracoid.s. 



Limuloids. 

 Rotifers. 



7. Subdivisions of the orders of the class of Worms. — On the 

 true method of grouping the typical (Branchiate and Abranchiate) 

 Annelids, I here make no suggestions. The Cystics are there 

 included with the Cestoids. If any of the simple Cystics are 

 really adults, they may possibly make a second subdivision of 

 the Cestideans. 



8. Subdivisions of the classes of Mollusks. — The ordinary Mol- 

 lusks include three orders, as usually given : (1.) Cephalopods, 

 (2.) Cephalates, and (3.) Acephals ; of which the first two corre- 

 spond to different grades of typical Mollusks, and the last is de- 

 gradational in its relations to the type, the species being imperfect 

 in the senses and means of locomotion. 



The Ascidioid Mollusks comprise (1.) Brachiopods, and (2.) 

 Ascidians, with perhaps the Bryozoans as the third order. If 

 the last, however, be made a third class, as already suggested 

 (though with hesitation), there is no third order, unless the in- 

 ferior of the compound Ascidians, having water-apertures to a 

 group of individuals instead of to each one, and the mouth-opening 

 of each usually radiated (the number of rays six), be regarded as 

 the third. This would make the orders, (1) Brachiopods ; (2) 

 Ascidians; (3) Incrustates ; the first two typical, the last degra- 

 dational and strikingly hemiphytoid. 



4. Conclusions. 



The preceding review of zoological classification appears to 

 sustain the following general conclusions. 



1. Number and typical relations of the subdivisions of groups. 

 I. The number of subkingdoms, classes, orders, and tribes, in 



