202 JURA. LUMINOUS ANIMALS. 



even in those depths, inconveniences similar to those 

 which bodies in a state of putrefaction cause on the sur- 

 face of the earth. It is also not improbable that the desire 

 which fishes appear to show of following luminous bodies, 

 arises from this natural instinct.* 



It has been remarked that those seasons in which the 

 water is most luminous, are most favourable to the herring 

 fishery. This may be explained by the circumstances 

 above detailed ; since the pursuit of the Medusae appears, 

 no less than the choice of places for spawning, to be a 

 motive for the migration of the herring, and for its appa- 

 rently capricious change of haunts. There is little doubt 

 that these animals form a principal part of its food ; and 

 were it not for the false notions of seamen on the subject 

 of luminous water, the fishermen would probably derive 

 advantage from following those indications which they 

 now neglect. But it is not surprising that this circum- 

 stance should have been overlooked, when it is considered 

 that the natural history of the herring is still involved 

 in almost absolute darkness.f 



* That some such notions as the preceding have prevailed, we have 

 a proof in a very outrageous simile of Cowley, where he compares his 

 mistress bathing, to a light : the quotation may amuse the reader who 

 is not conversant with the metaphysical poets. 



" The fish around her crowded as they do 

 To the false light that treacherous fishes show." 



f It can admit of no doubt that the Medusae are eaten by the supe- 

 rior classes offish, as they are frequently found with portions torn oft"; 

 and the coal fish, which swim^near the surface, may often be seen 

 engaged in this operation. Yet the animal matter which they contain 

 bears a very small proportion to their bulk. In some rude experiments, 

 made at sea, on boiling down an hundred pounds of Medusa cruciata, 

 no gelatine was obtained, and but a very small portion of coagulated 

 albumen. The residue was almost entirely - sea salt. Those were 

 purposely selected of which the stomachs were empty. It is probable 

 therefore that, with the exception of the small quantity of fibre in their 

 swimming muscle and stomach, they consist entirely of a very fine 

 cellular membrane, minutely divided and filled with water. As Philip II. 

 imagined offish in general, they seem little else but coagulated water. 



