1899] LIFE HIGH AND: LOW 165 
population when the nature of the bottom deposit changes. It has 
been a laborious piece of work, executed with patient carefulness, and 
the results though not startling are certainly valuable.’ 
Since the principal object of the investigation was to study the 
relation of the fauna to the bottom-deposit, the area selected for 
examination was so chosen that the general physical conditions were 
uniform apart from the nature of the deposits, and the amount of 
disturbance of the bottom water by the action of waves was relatively 
small. The chief results to be gained by carefully scanning the 
numerous tables—the drawing up of which must have meant a large 
amount of work—relate to the suitability of certain kinds of ground 
for certain kinds of animals, but apart from this the memoir is also 
interesting because of the numerous notes on the habits of the animals 
and for its analysis of the environmental conditions. 
The physical conditions, the variations of which influence the life 
of bottom-living species, are capable of definite statement, and for the 
most part of accurate measurement. They are— 
1. The constitution of the sea-water. 
The nature of the bottom-deposit. 
The movements of the water, due to 
(a) wave action, 
(6) currents, 
(ec) tides. 
4. The temperature of the sea-water. 
5. The pressure, varying with the depth of water. 
6. The amount of light which penetrates to the bottom. 
The external biological conditions influencing the distribution of 
any bottom-loving organism, due to the existence at the same time ot 
other living organisms, are often of a complicated nature. 
1. One organism may exert an advantageous influence upon another. 
(a) By serving as its food-supply ; 
(b) By serving as a fixed base to which it may attach itself; 
(c) By serving as a movable base, and thus extending the 
area over which a fixed organism can collect its food- 
supply ; 
(d) By bringing supplies of food to the other organism as 
well as to itself, either by setting up a current, or in 
some other way ; 
(e) By affording the other organism means of protection or 
concealment from its enemies. 
2. One organism may exert a disadvantageous influence upon 
another. 
(a) By preying upon it ; 
bo 
oN) 
* “On the Fauna and Bottom-deposits near the Thirty-fathom Line from the Eddystone 
Grounds to Start Point,” Journ. Marine Biol. Ass. v. June 1899, pp. 365-542, 15 charts 
and 7 tables, 
