86 COMPARATIVE ANATOMY. 



are largely supplied with nerves, as well as from the obser- 

 vation that portions of the brain (gray matter of cerebral 

 hemispheres) and the terminal branches of certain nerves of 

 sensation (Paciriian corpuscles, Wagnerian corpuscles, con- 

 junctival corpuscles) resembled in construction electrical ma- 

 chines. But it was afterward found that nerve power could 

 not take the place of an electrical current. A string tied 

 round a nerve produces paralysis of motion beyond the ob- 

 structed point; but no ligature upon a metallic conductor 

 can obstruct an electrical current. If the nerves going to a 

 muscle be cut, the muscle is rendered incapable of contract- 

 ing. If the nerves going to an electric organ be severed, 

 the organ can no longer give out electric discharges. But if 

 the dead organ be taken, electricity can be developed from 

 it in the same manner as it can in an organic voltaic pile. 

 Animal electricity is essentially a life product. 



ANIMAL PHOSPHORESCENCE. 



Animal phosphorescence is confined to the Invertebrata. 



The majority of phosphorescent animals are marine. Con- 

 spicuous among these forms is the Noctiluca miliaris. This is 

 a small sub-rounded animal, about one-sixtieth of an inch 

 in diameter, composed of a structureless and somewhat dense 

 integument, and furnished with a long sub-cylindrical filiform 

 tentacle. Mouth simple, situated upon under surface of body 

 and behind tentacle ; from its base a very delicate filament 

 protrudes, which exhibits a rapid undulatory motion. In ad- 

 vance of mouth, and between it and tentacle, a horny-looking 

 bifid ridge is present, the so-called tooth. (Huxley.) Intes- 

 tine and anus not determined. The i nucleus' a strongly re- 

 fracting oral body of about 4$-$ inch in length. By some 

 considered a radiate, Noctiluca is more properly classified 

 with the Protozoa. 



Among other animals possessing this property are many 

 coelenterate radiates, and some echinoderms; Salpa and Pyros- 

 oma among molluscs; and various Infusoria, Annelida, and 

 Crustacea. Among light-bearing terrestrial forms may be 



