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 algo, 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 tried 
by Pourtalés. 
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 twilight at a 
depth of about fifty fathoms, passing into a darker regioni 
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 
1 Professor Verrill has made the rather there may be a soft green light, not unlike 
startling suggestion, that in deep water a pale moonlight. 
