﻿228 Proceedings of the Royal Physical Society. 



marked, and is therefore worthy of special consideration. 

 If the observations were continued long enough, we should 

 no doubt recognise seasonal variations in the fauna. It 

 would be necessary to analyse the causes of such variations 

 and correlate them if possible with variations in temperature, 

 atmospheric conditions, salinity, and food-supply, as well as 

 with breeding habits, normal life-cycle, etc. Slow secular 

 changes might be revealed by observations extending over 

 many years. 



How are our observations to be directed to these ends? We 

 must start with a careful study of the physical characters of 

 our chosen area, its extent, aspect, shelter, slope, the nature of 

 the ground, the tidal currents, the salinity of the water, and 

 so forth. We must then divide up the beach into zones, 

 determine the area exposed to the action of fresh water, 

 and classify the " positions" to be recognised. 



We must make systematic collections representative of 

 the complete fauna, on many different occasions during the 

 year, noting on each occasion the conditions of weather and 

 tide. In making such collections, special attention must be 

 directed to the state of maturity the proportion of mature 

 and immature individuals, and the extent of the breeding 

 season, in order to gain as full a knowledge as possible of 

 life-histories. 



In order to test the actual working of the method outlined 

 here, we made, last August, a systematic series of observa- 

 tions extending over a period of three weeks. We selected 

 for the purpose a small bay, which was within easy reach of 

 the Marine Biological Station at Millport. Here we made 

 collections and observations daily. From the data obtained 

 in this short period, and from the study of a single area of 

 very limited extent, we do not attempt to draw conclusions 

 of general ecological significance. We have investigated 

 methods rather than zoological facts. 



We proceed to describe the area chosen, and the methods 

 adopted for collecting and recording. 



It may be mentioned, in passing, that this area was not 

 a rich one from the collector's point of view. 



