THE PHYSIOLOGY OF DEEP-SEA LIFE. 305 



In fishes brought up from deep water, the swimming-bladder 

 often protrudes from the mouth, the eyes are forced out of their 

 sockets, the scales have fallen off, and they present a most dis- 

 reputable appearance. 



Regnard's experiments on the effects of pressure — experi- 

 ments producing a pressure fully as great as that to which they 

 are subject in deep water — indicate that algae, infusoria, mol- 

 lusks, worms, and even fishes, are thrown by pressure into a 

 torpid condition, from which they recover after a time when 

 placed again in normal conditions. If the pressure is very 

 powerful and long-continued, it proves fatal to fishes. 



But few experiments have been made to ascertain the depth 

 to which light penetrates. They seem to show that a depth of 

 about two hundred fathoms is the lower limit. Forel proved 

 that in the Lake of Geneva photographic plates remained sensi- 

 tive to between thirty and fifty fathoms, a depth at least four 

 times that at which the presence of a white disk sunk below the 

 surface could be detected, according to the experiments ti'ied 

 by Pourtales. 



These experiments, however, do not determine the limits at 

 which very faint rays of various colors may reach considerable 

 depths. Secchi found that red, yellow, and green successively 

 disappeared, while blue, indigo, and violet remained quite bright 

 at a depth of about forty fathoms. This may explain why, 

 among so many of the deep-sea echinoderms and other animals, 

 violet pigments seem to be the most prominent ; yet it has been 

 assumed that the presence of red and carmine among abyssal 

 Crustacea and the like proves that the red rays have the greatest 

 penetration. We may imagine a reddish yellow twihght at a 

 depth of about fifty fathoms, passing into a darker region 

 near the hundred-fathom line ; and finally, at two hundred 

 fathoms, a district where the light is possibly that of a bril- 

 liant starlight night. ^ 



M. Edouard Sarasin and Professor Fol recently made an inter- 

 esting report of the experiments conducted by the committee of 

 the Physical Society of Geneva to ascertain the transparency of 



^ Professor Verrill has made the rather there may be a soft greeu light, uot unlike 

 startliug suggestion, that in deep water a pale moonlight. 



