158 Puget Sound Marine Sta. Pub. Vol. 1, No. 14 



II. HABITATS, MATERIAL AND%METHODS. 



1. General 



The Puget Sound Marine Station is located in a situation very fa- 

 vorable to the study of the problem at hand because of the diversity 

 not only of shallow water habitats, but of depth conditions. Within a 

 half mile from the station building it is possible to secure animals from 

 over 150 meters of water practically free from algae, which are a source 

 of difficulty in respiration work and various physiological operations. 

 There are also various kinds of habitats in shallow water. Bays of 

 varying degrees of exposure, with various sized bottom materials, rocks 

 exposed to the full sweep of the waves and rocks protected from severest 

 wave action. The greater part of the material studied was collected 

 from a definite area north of Brown Island, shown in the map {plate 29, 

 p. 174). Here the following belts may be recognized: 



2. Habitats 



The Shore Belt lies between high tide and average low tide. ]\Iean 

 tide is nearly a meter below average low tide. The average low tide 

 is marked by the lower limit of such plants as Fucus and of shore 

 barnacles and by the upper limit of Ulva. It represents the belt usually 

 submerged and uncovered twice daily. On the shore of Brown Island 

 the shore belt represents about three meters vertical distance. The 

 shore is steep and covered with broken rocks. Depressions in the solid 

 rock often hold water which teems with small Littorina, purple shore 

 crabs, and sometimes small fish (Oligocottus). The water in these pools 

 often goes as high as 27° C. on sunny days. The rocks become quite 

 warm in the sunshine. Barnacles and limpets are sometimes fully ex- 

 posed to the sun. The incoming tide water often is 20° to 24° C. among 

 the warm rocks under which the shore crabs are numerous 



The Laminarian Belt (-f-1 to — 20 meters) reaches from average 

 low tide to the lower limit of the Laminariaceae. Most of the animals 

 appearing exposed at extreme low tides are distributed throughout this 

 l)elt. The broad leaved green algae afford shelter for many forms that 

 avoid exposure to the sun. The presence of these broad leaved algae 

 makes a striking contrast between the physical conditions of this kind 

 and all other belts. Tide and wave action keep the water well mixed, 

 and light penetrates to the bottom of this belt with a noteworthy decrease 

 in red rays only. Fol, the Swiss naturalist who worked in a diving suit 

 in the Mediterranean, found that at 10 meters light disappeared quite 

 suddenly early in the afternoon long before sunset. At 20 meters in 

 the Harbor of Funchal, Madeira Island, in June the Prince of Monaco 



