545 
DEEP SEA LIFE IN THE BAY OF BENGAL. 
[Extracts from a paper read before the Microscopical Society of Calcutta, on 
11th September, 1893, by Dr. A. W. Alcock.] 
Tn a previous lecture, which I had the honour last year of delivering before 
this Society, I gave an account of the physical geography of the sea basins and 
seas of the Indian region, and of the various technical methods by which the 
facts of marine physiography, or hydrography, have been elucidated. To-day 
I have before me the much simpler task of exhibiting a few of the inhabitants 
of these deep sea basins, of explaining some of the more obvious peculiarities 
of their structure, and of offering a few suggestions as to the relations which 
these peculiarities of structure bear to the peculiarities of the habitat in which 
the animals are found. 
Ti is hardly necessary for me to remind you that peculiarities in the form 
of animals are largely the outcome of peculiarities in their environment or 
habitat. We express this fact by saying that such or such an animal is exactly 
adapted to its environment. In the case, for instance, of animals that live in 
dark caves—such as the Mammoth Cave of Kentucky—we find that the eyes 
are wanting, Here isa cray fish (Cambarus pellucidus) from the Mammoth 
Cave: it has eye-stalks just like other cray fish, which proves that it is descend- 
ed from a well-eyed form, but there are no eyes at the end of the eye-stalks, 
Other species of Cambarus which do not live in the dark possess eyes. Now 
why should Cambarus pellucidus have lost its eyes? Because eyes are no 
longer necessary ; they have fallen into disuse. Being of no service to their 
possessors they are not acted upon by natural selection, for in the dark an 
animal with eyes has no better chance of surviving than an animal without 
eyes, Furthermore, eyes are delicate organs and extremely liable to injury : 
moreover they are large and vascular structures, and require a large amount 
of blood. Now, so long as the eyes are highly useful to their possessor, it so 
to speak “‘ pays” to protect them from injury, and to keep them supplied with 
blood ; but when they become useless it is in the highest degree wasteful to 
expend upon them the nourishment and care that might be much more ad- 
vantageously bestowed upon some organ more useful to an animal living in 
the dark,—such as an organ of smell or an organ of touch: under such con- 
ditions we may expect an eyeless species to be gradually developed—such as 
this Cambarus, and the blind fish and the blind amphibian, along with which 
it lives. Cambarus, then, is an excellent and extreme illustration of the truth 
of the fact, that peculiarities in the environment of an animal are largely 
answerable for peculiarities in the structure of that animal. 
Beside peculiarities in the inorganic environment there are other powerful 
factors that influence the shapes and structure of animals, One of the prin- 
cipal of these is the necessity for getting food to eat in the face of a multitude 
of hostile competitors of the same and of other species. 
