338 ESSAY ON CLASSIFICATION. 



CL. 2. POLYPI (Intestine animals). Mouth with lips and tentacles, 

 to seize. 



CL. 3. ACALEPH.E (Lacteal animals.) Body traversed by tubes simi- 

 lar to the lymphatic vessels. 



Cycle II. Circulative Animals.=: Mollusks. Essential character: intes- 

 tine and vessels. 



CL. 4. ACEPHALA (Biauriculate animals). Membranous heart with 

 two auricles. 



CL. 5. GASTEROPODA (Uniauriculate animals). Membranous heart 

 with one auricle. 



CL. 6. CEPHALOPODA (Bicardial animals). Two hearts. 



Cycle III. Respirative Animals. = Articulata. Essential character: in- 

 testine, vessels, and spiracles. 



CL. 7. WORMS (Skin animals). Respire with the skin itself, or part 

 of it ; no articulated feet. 



CL. 8. CRUSTACEA (Branchial animals). Gills or air tubes arising 

 from the horny skin. 



CL. 9. INSECTS (Tracheal animals). Tracheas internally; gills ex- 

 ternally as wings. 



2nd Grade. FLESII ANIMALS ; also called 7/effcZ-aniinals = Vertebrata. Two 

 cavities of the body, surrounded by fleshy walls (bones and 

 muscles) enclosing nervous marrow and intestines. Head with 

 brain ; higher senses developed. Characterized by the deve- 

 lopment of the animal systems, namely, the skeleton, the 

 muscles, the nerves, and the senses. 



Cycle IV. Carnal Animals proper. Senses not perfected. 



CL. 10. FISHES (7?o?ze-animals). Skeleton predominating, very much 



broken up ; muscles white, brain without gyri, tongue without 



bone, nose not perforated, ear concealed, eyes without lids. 

 CL. 11. REPTILES (3/wsc/e-aniuials). Muscles red, brain without 



convolutions, nose perforated, ear without external orifice, eyes 



immovable, with imperfect lids. 

 CL. 12. BIRDS (^Verye-animals). Brain with convolutions, ears open, 



eyes immovable, lids imperfect. 



Cycle V. Sensual Animals. All anatomical systems, and the senses per- 

 fected. 



CL. 13. MAMMALIA (*Sfe?ise-anirnals). Tongue and nose fleshy,ears open, 

 mostly with a conch, eyes movable, with two distinct lids. 



The principles laid down by Oken, of which this classi- 

 fication is the practical result for Zoology, may be summed 

 up in the following manner : The grades or great types 



