APPENDIX. 89 



plex in land animals. The organ of seeing is diffe- 

 rent in those animals which are formed to see in 

 water, and in those which see in air ; it differs again 

 in those which are to see with little or much light ; 

 all those peculiarities are illustrated by preparations. 

 The pigmentum nigrum in some fishes resembles 

 polished silver ; in ruminating animals, at the bottom 

 of the eye it has a greenish hue ; in the lion and cat 

 kind, a portion of the bottom is white, but as a ge- 

 neral principle, the colour of the pigmentum is the 

 same as the rete mucosum of the skin of the animal, 

 being white in white animals, and black in very dark 

 ones. 



After the brain and senses, are arranged the cellu- 

 lar membrane and animal oils, which are followed by 

 the external coverings. These are divided into the 

 different kinds, as hair, feathers, scales, &c., with 

 the rete mucosum, or that membrane which is inter- 

 posed between the true and scarf skin, for the pur- 

 pose of giving the peculiar colour. Added to these 

 are the parts peculiar to different animals for offence 

 and defence, as spurs, hoofs, horns, stings, and also 

 electric organs. There follow next such peculiar 

 structures as occur in certain tribes of animals, as 

 the air-bladders in fish, &c. 



The fourth class begins with the animals which have 

 no distinct parts allotted for generation, that power 

 being diffused over the whole animal. In these the 

 young grow out of the old, as in the coral and 

 polypi ; and next in order come tho hermaphrodite 



