106 



SYNOPTICAL 



I. INVERTEBRATA 



ZOOPHYTES. 



actinise, 



Polypi, 

 medusx. 



DIGESTION. 



Food received with- 

 out mastication into 

 intestinal cavity sim- 

 ply hollowed out in 

 the animal mass, and 

 digested by a mucous 

 fluid exhaling from 

 its coats 



Liver none, or doubt- 

 ful. Single aperture 

 serves for both mouth 

 and vent. 



ABSORPTION I AERATION. 



of Chyle. I The nutritive fluid, 



By simple imbibitionin thus generally per- 

 into the pores of thecolating the system, 



animal mass. 



appears to require 

 only more contact 

 with the aerated wa- 

 ter surrounding the 

 external surface, in 

 the actiniae ; but in 

 the medusae, a system 

 of ramifying vessels, 

 having external open- 

 ings, conveys the wa- 

 ter through the body : 

 these may be called 

 aquiferous tracheae. 



RADIATED 

 ECHINODERMATA 



Starfish, encrinites, 

 echini, holothuria. 



A manifest liver is 

 observable in all this 

 division ; and the e 

 chini have an appa- 

 ratus for mastication 

 attached to the mouth 

 which is distinct from 

 the vent and long 

 convolutions of the in 

 testine ; but in these 

 respects the star fish 

 are nearer to the 

 lower class. 



Simple imbibition. 



By means of a sys- 

 tem of aquiferous tra- 

 cheae, which bring the 

 aerated water in con- 

 tact with the nutritive 

 fluid. 



ACEPHALOUS 

 MOLLUSCA. 



A. Without shells ; 

 biphori and ascidiae. 



B. All the animals 

 inhabiting bivalve 

 shells. 



No distinct masti- 

 cation ;stomach,liver, 

 and intestine. 



Vent always pos- 

 terior. 



The ordinary ves- 

 sels act also as ab- 

 sorbents of the chyle. 



By means of vascu- 

 lar branchiae. In the 

 naked acephala lin- 

 ing the inside of a 

 sac between the out- 

 er mouth and the 

 phar}'nx. In the con- 

 chifera disposed in 

 laminated fringes 

 skirting the sides and 

 lower margin. 



CEPHALOUS 



MOLLUSCA, 



xoith distinct heads. 



Distinct teeth for 

 mastication in many 

 genera ; in others a 



As in the last di- 

 vision. 



Mostly inhabiting prickly tongue, 

 univalve shells ; also! Stomach, and oc- 

 cuttle fish. casioi.ally gizzard. 



I Liver and long con- 

 Ivoluted intestine ; 

 vent variously placed; 

 but in the univalves, 

 on the same side with 

 'the spire of the shell. 



Most breathing wa- 

 ter by branchiae of 

 various forms ; but 

 the pulmobranchia 

 breathe air by a pul- 

 monary cavity. 



