007 
and has large eyes, Avliieh was caught, having swallowed another 
fish many times larger and heavier than itself — the ventral body- 
wall, with the stomach, protruding very far beyond its usual 
position. 
A large proportion of the deep-sea fauna belongs to groups, none 
ot the members of whicli (in the adult condition) possess eyes, 
such as Sponges, Actinozoa, Polyzoa, and IJrachipods ; but there 
are others, the members of which are, under ordinary circumstances, 
endowed with organs of vision, which, at abyssal depths, are 
represented by forms either totally blind, or with eyes which have 
become rudimentary and functionless. Of these may be mentioned 
AV orms, the greater number of Avhich are blind at depths greater 
than five hundred fathoms; among the Crustacea, Petalopthalamus, 
one of the i\ry8ida) found at a depth of from eight hundred to 
sixteen hundred fathoms, which pos.scsses long eye-stalks without 
eyes, but with largo spheroidal chitinous plates in their place, and 
Avithout any trace of visual apparatus. In some of tlio deep-sea 
Crayfish the eyes are functiouless, and in Willemcesia — allied to 
tlio Pock Lobster — Avanting ; and numerous other similar instances 
might bo given. Man}’ deep-sea fish are blind; but there are some 
Avhich are provided Avith extremely large eyes ; Avhile in others the 
eyes are of the normal character, or even smaller than usual. In 
the case of some Schizopods, Avhich are found at a dejitli of sixteen 
hundred iathoius, accessory eyes have been developed Gnatho- 
phansia has an eye on each second maxilla or third jaAv. Euphansia 
has eight accessory eyes on the ventral surface of its thorax and 
' abdomen, Avhilo Thysanopoda has eight pairs. A gigantic Ostracod, 
an inch long, Avith large eyes, A\’as obtained from a great depth ; 
and an Amphion, the larval sUage of a form allied to Palinurus, 
the Pock Lobster, has eyes Avhich arc borne on stalks as long as 
the whole body of the animal. 
The connection of pelagic animals Avith the subject is not at 
first sight obvious. A largo proportion of these, hoAvever, are 
nocturnal in their habits. Weismann has'shoAvn that nearly the 
entire fauna of the Lake of Constance oscillates in level Avith 
the increase or diminution of light. It does not descend during 
o O 
the day to a depth greater than that at which sensitized paper is 
affected, but at night it reappears on the surface. The eyes of 
such animals, Avhich are so constructed as to enable them to see 
