96 The Rev. P. Keith on the Structure of Animals, 



the coast with a flood tide, floating or drifting on the surface 

 of the wave, sometimes singly, and sometimes in multitudes, 

 under the semblance of a large lump of jelly, — in Medusa 

 auritanot less than three or four inches in diameter, — with their 

 tentacula spreading around them. They emit a phosphorescent 

 light in the night, and when voyaging in large shoals illumi- 

 nate the surface of the deep. They sting the hand that touches 

 them, and cause a tingling pain. 



Srdly. The third order includes corals, corallines, and 

 sponges, in which a sensitive body surrounds an insensible 

 stalk, or is inclosed in an insensible covering, — stony, crus- 

 taceous, or horny ; not constructed by the animal itself, but 

 congenital with it; not phosphatic, but calcareous, — stirps 

 radicata, — attached. The former varieties occur in the Gor^ 

 gonicE, the latter in the TuhijporcB and Celleporcc, 



4thly. The fourth order is that of the Polypi^ the body being 

 a mere bag of jelly attached to a stirjps libera^ as in the case of 

 the sea-feather ; or wholly unattached, — corpus liberum, — with 

 arms radiating from the mouth. Some of them you may turn 

 inside out, like the finger of a glove, and the animal shall still 

 live. You may cut them into as many pieces as you please, and 

 each piece will become an entire animal. Hydra viridis is a 

 good example. 



5thly. Finally, the fifth order is that of the Infusoria, which 

 consist merely of a small and pulpy globule, capable of a brisk 

 and spontaneous motion, but furnished with no external organ 

 whatever. If a drop of water taken from a ditch or pond in 

 which vegetable substances are becoming putrid, or if a drop 

 of rain water that has stood exposed to the weather for a few^ 

 days, is put upon the stage of a good microscope, and the eye 

 applied to it, you may see hundreds of them frolicking in that 

 single drop, like fishes in the ocean. 



Thus life assumes a great variety of different aspects, ac- 

 cording to the tribe or family in which we contemplate its 

 phasnomena ; and thus a scale of degrees, from man down- 

 wards, is evident even from the contemplation of the external 

 structure. In man you have the several parts of the body the 

 most distinctly marked, — the head, the neck, the trunk, the 

 limbs; and the organs of sense the most fully developed, — the 

 eye, the ear, the nose, the palate, the touch ; with the peculiar 

 conformation of the foot and of the hand, — the former serving 

 as a basis to support the body in the erect posture, and the lat- 

 ter as an instrument adapted to the thousand different purposes 

 for which man may have occasion to employ it, — whether in the 

 fine arts, as in music, drawing, painting, sculpture ; or in the 

 domestic arts, as in the fabrication of clothing or the construc- 

 tion of machinery ; or as in the operations of agriculture ; or 



