16 : DEEP SEA FISHES. 
Most often the eyes of bathybial animals are larger than those of their kin- 
dred near the surface. Entire absence of light would have favored the de- 
terioration and loss of the eye, but the eyes have become rudimentary in 
hardly a dozen of the multitude of known deep sea species. The list of the 
so-called blind forms of great depths includes Benthobatis Moresbyi Ale., Typh- 
lonus nasus Giint., Aphyonus gelutinosus Giint., Aphyonus mollis G. B., Bara- 
thronus bicolor G. B., Alexeterion Parfaiti Vaill., Tawedophidium Heatii Alc., 
Sciadonus pedicellaris sp.n., Leucicorus lusewsus sp.n., Dysomma bucephalus Ale., 
Dysommopsis muciparus Ale., and Myzine circifrons sp. n. Other species of 
Myxine should be included in a complete list of marine blind fishes, but the 
loss of the eyes in this genus is to be attributed to parasitic habits rather 
than to bathybial conditions. Benthobatis, a recently discovered Torpedo, is 
the only blind Selachian known. Eight of the others on the list are Brotu- 
loids, and two, Dysomma and Dysommopsis are Murzenoids. In all these 
cases, Myxine being excepted, the eyes have become rudimentary and are 
more or less inefficient as visual organs. The case of Leucicorus is peculiar 
in that the blindness is comparatively recent, if indeed the loss of the eye 
is not an old age character and subsequent in the individual to an ordinary 
useful organ in the early stages. Nearly all of the species on the list, ex- 
cepting only perhaps Sciadonus and Myxine, dwell in the ooze, and on all 
of them compensation for the loss of sight appears in an inordinately devel- 
oped Lateral Canal System. On Sciadonus, Plate F, figure 4, in addition to 
the increased prominence in the development of the system there are con- 
siderable sensory developments on the fins. This genus is more likely to 
hav& the habit of swimming freely at a distance from the bottom. The 
greatest amount of differentiation of the visual organs known among bathiy- 
bial fishes occurs on Ipnops; here the ocular structures cover the whole 
top of the head and depart radically from the common definition of eyes, 
but, as Mosely has shown, they still retain the function of sight. Appar- 
ently they have the additional functions of flashlights and reflectors; they 
are to be seen on Plate H, figures 2 and 2a, as they appear on a fresh speci- 
men. ‘Two species of this extraordinary genus are now known, J. Muwrrayi 
and J. Agassizi’, the latter from the present collection. Commonly in the 
modification of the eye the outer structures are the first to deteriorate, 
while the ball remains and gradually becomes very minute, as in Aphyonus 
and others, before final disappearance. In Barathronus bicolor, however, the 
ball has disappeared and the large orbit has undergone a modification which, 
