COMPARATIVE ANATOMY. 



perfectly known, when the Swedish na- 

 turalist first promulgated his arrange- 

 ment. But the labours of subsequent zoo- 

 logists, and particularly those of Cuvier, 

 have succeeded in establishing such strik- 

 ing and important differences in their for- 

 mation, that a subdivision of the Linnaean 

 classes became indispensably necessary. 

 The insects of Linnaeus are divided into 

 Crustacea and insecta : and the verrnes of 

 the same author form three classes : tftz. 

 Molluscu, Verraes, and Zoophyta. 



The Mollusca derive their name from 

 the soft fleshy nature of their body. This 

 class includes those pulpy animals, which 

 may either be destitute of an external 

 covering, when they are called mollusca 

 nuda, as the slug ; or may be inclosed in 

 one or more shells, as the snail, oyster, 

 Sec. when they are termed testacea. 



The animals of this class have no arti- 

 culated members : they have blood-ves- 

 sels, and a true circulation ; they respire 

 by means of gills ; they have a distinct 

 brain, giving origin to nerves ; and a spi- 

 nal marrow. 



1. Sepia, cuttlefish. 



2. Argonauta. 



3. Nautilus. 



4. Limax, slug. 



5. Aplysia. 



6. Doris. 

 . 7. Clio. 



8. Patella, limpet. 



9. Helix, snail. 



10. Haliotis, Venus's ear. 



11. Murex, caltrop, or rockshell. 



12. Strombus, screw. 



13. Buccinum, whelk. 



14. Ascidia. 



15. Thalia. 



16. Ostrea, oyster. 



17. Solen, razorshell. 



18. Cardium, cockle. 



19. Mytilus, muscle, &c. &c. 



Cuvier classes the numerous genera of 

 this order under the three following di- 

 visions : 1. Cephalopoda, (from xfpctby 

 the head, and KX$ the foot) which have 

 their organs of motion placed round the 

 bead; 2. Gasteropoda, (from y^Sff, the 

 belly, and vx^^ such as crawl on the 

 belly ; and 3. Acephala, (from #, priva- 

 tive, and xe<pesAj,) which have no head. 

 The three first genera belong to the first 

 division ; the ten succeeding ones come 

 under the second ; and the remainder ex- 

 emplify the last order. 



According as the shell of the testace- 

 ous mollusca consists of a single convo- 

 luted tube, or of two or more separate 

 pieces, they are called cochleae bivalves^ 

 multivalves, &c. 



Crustacea possess a hard external ca- 

 vering, and numerous articulated mem- 

 bers ; a long nervous chord, beset with 

 ganglia ; compound eyes ; antennae and 

 palpi like those of insects ; a heart and 

 circulating vessels, and gills ; teeth in the 

 cavity of the stomach. 



1. Cancer, crab, lobster, crayfish, 



shrimp. 



2. Monoculus. 



Insects have articulated members and 

 antennae. Those which fly are subject 

 to what is called a metamorphosis ; they 

 pass through certain intermediate states 

 of existence before they assume the last 

 or perfect form. From the egg proceeds 

 the larva, or caterpillar : this changr s to 

 the chrysalis, nympha, or aurelia, from 

 which the perfect insect is produced ; 

 nervous system consisting of a chord be- 

 set with ganglia ; no heart nor blood-ves- 

 sels ; respiration carried on by means of 

 tracheae. 



Order I. Coleoptera ; having a hollow, 

 horny case, under which the wings arc 

 folded. 



1. Scarabaeus, beetles. 



2. Lucanus, stag-beetle. 



3. Dermestes. 



4. Coccinella, lady-bird. 



5. Curculio, weevil. 



6. Lampyris, glow-worm. 



7. Meloe, Spanish-fly. 



8. Staphylinus. 



9. Forficula, earwig. 



II. ffemiptera ; four wings, either 

 stretched straight out, or resting across 

 each other. 



1. Blatta, cockroach. 



2. Gryllus, locust, grasshopper. 



3. Fulgora, lantern-fly. 



4. Cimex, bug, &c. 



III. Lepidoptera ; soft hairy body, and 

 four expanded wings. 



1. Papilio, butterfly. 



2. Sphinx, 



