SKELETON IN THE INVERTEBRATA. 



11 



Division. 



II. DIPLO-NEURA 

 vel ARTICULA- 

 TA. 



III. CYCLO-GAN- 

 GLIATA vel 

 MOLLUSCA. 



IV. SPINI-CERE- 

 BRATA vel 

 VERTEBRATA. 



Class. 

 f 6. Entozoa - 



7. 

 8. 

 9. 

 10. 

 11. 

 12. 

 113. 

 fl4. 

 115. 

 {jft. 

 117. 



Lis. 

 f19. 



I 20. 

 <2l. 



| 22. 

 123. 



Rotifera - 



ClRRHOPODA 

 ANiNELIDA - 



Myriapoda 

 Insecta - - 

 Arachnida 

 Crustacea 

 Tdnicata - 

 conchifera 

 Gasteropoda 

 Pteropoda 

 Cephalopoda 

 Pisces - - 

 Amphibia - 

 Reptilia - 

 Aves - - 

 Mammalia 



Exam. Intestinal worms, hyda- 

 tids. 



Patella. 



Barnacle, triton. 



Earth-worm, leech, 



Scolopendra. 



Bee, butter-fly. 



Spider, scorpion. 



Lobster, crab. 



Ascidia intestinalis. 



Muscle, oyster. 



Slug, snail. 



■ Clio, hvalosa. 



Cuttle-fish. 



Salmon, shark, eel. 



Frog, toad, proteus. 



Tortoise, lizard, serpent. 



1 Eagle, heron, duck. 



Man, kangaroo, whale. 



Many other arrangements of the animal kingdom have been pro- 

 posed by different zoologists; some, as Linneeus, founding their basis 

 of classification on the vascular and respiratory systems, and others on 

 the peculiarities afforded by the generative organs. Aristotle divided 

 all animals into those with, and those without red blood; and 

 Lamark into the apathic, the sensitive, and the intelligent. 



CHAPTER II. 



SKELETON IN THE INVERTEBRATA. 



General observations. — The skeleton gives figure, strength, and 

 solidity to the entire frame ; it serves as a basis of support to the 

 soft parts, forms levers of locomotion, and encloses cavities to pro- 

 tect and defend the most delicate and important organs. Its use, 

 however, being chiefly of a mechanical nature, it will be found to 

 vary much, according to the respective wants, habits, and instincts 

 of animals. In all the operations of nature we find that there is a 

 rigid economy observed ; the means employed are such only as 

 are required, and always the most simple by which the intended 

 purposes can be accomplished. Hence we shall not be surprised to 

 meet with infinitely varied modifications of skeleton throughout 

 the widely extended range of the animal world. The chemical 

 composition of this solid frame-work presents some variety. For 

 instance, silica is found in the lowest forms of the radiata ; carbo- 

 nate of lime in the molluscous animals; carbonate and phosphate of 

 lime in the articulata ; and phosphate of lime in the organised skele- 

 tons of the vetebrata. This frame-work is sometimes placed external 

 to the soft parts, and in others it is internal to them. In no instance 

 do we meet with a bony skeleton except in animals possessed of 



