﻿232 Proceedings of the Royal Physical Society. 



which it was cut off by a promontory of rock. Naturally, 

 only the two positions, " under stones," and " in substratum," 

 are affected by the percolation of fresh water, when the tide 

 is out, and in our experiment we studied the distribution of 

 the fauna only under low-tide conditions. 



Description of a Collecting Excursion or " Haul!'— The 

 following data were invariably recorded before commencing 

 work : — 



Date. 

 Time. 



Weather conditions. 

 Temperature of air and water. 



Condition of humidity as shown by state of rock 



surface. 

 Wind. 

 Barometer 

 State of tide. 



Collections were then made from definite positions in 

 definite zones or subzones, and conspicuous features 

 of the distribution of abundant species were noted on 

 the spot. 



Recording. — The usual method was to record on the spot 

 all forms readily identified at sight, with notes on their 

 relative abundance, and on any other points of general 

 ecological interest, e.g., feeding habits, activity, and general 

 behaviour, then to take carefully -labelled living samples of 

 all material requiring fuller investigation. Such investigation 

 might involve washing of weeds, decanting of sand and mud, 

 and the microscopic investigation of surface fauna of movable 

 stones. 



This material was taken to the Marine Station and worked 

 up as soon as possible — a very important point, for many 

 species are not readily preserved in a state in which they 

 can be identified with certainty {e.g.. Protozoa, Hydroids, 

 Actiniae, Turbellaria, Nemertines, Compound Ascidians, etc.). 



Species not identified at once were carefully fixed and 

 transferred to suitable preserving fluids, a label being 

 enclosed with each sample. The same procedure was 



