l88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I28 



creased in numbers by predators. When the food is gone the preda- 

 tors decrease in numbers, and then their prey increases in numbers. 

 The time of dredging in relation to this cycle would affect the number 

 of certain species. 



Still other factors have a bearing on the number of species found 

 in any locality. When larvae settle out of the plankton to become 

 bottom dwellers they may scatter, or they may settle in large numbers 

 in a small area. Sometimes the bottom is unsuited for that particular 

 species; or, if the bottom is suitable, conditions existing at the time 

 of settling influence the number that survive. Under favorable con- 

 ditions a large number of individuals of a species may become estab- 

 lished, but if conditions are adverse only a few survive even though 

 a large number of larvae of that particular species are settling to 

 the bottom. For instance, if the bottom is already well populated, 

 fewer larvae can become established than if the bottom were sparsely 

 populated. Also the presence of large numbers of other bottom- 

 dwellers that feed on settling larvae will greatly reduce the species. 



The futility of trying to collect weight-numbers data for a locality 

 is well demonstrated by the results of the investigation at Point Bar- 

 row. Such data for the entire rubble zone in 1949 would be entirely 

 different for the same area in 1950 after the deposition of mud dur- 

 ing the fall of 1949. The animals found at depths of 100 to 200 feet 

 in 1948 and 1949 were not the same as those found at the same depths 

 in 1950. A station that yielded a certain fauna one summer might 

 yield an entirely different fauna a year or two later after it had been 

 gouged out by an ice floe. 



An enormous amount of time and dredging is required to acquire 

 weight-numbers data, and it seems much more to the point to learn 

 more about the animals themselves — how and on what they feed, 

 how and when they reproduce, how fast they grow, how long they 

 live. Production of food in the economy of the sea depends on the 

 rate of reproduction and the rate of growth and these characteristics 

 are too often neglected in order to present pretty pictures of animals 

 on the ocean bottom in an attempt to illustrate relative abundance and 

 "dominance." 



In certain instances in treating the individual species in the "Dis- 

 cussion of Animals by Phyla," a comparison or contrast is made with 

 the same species from Greenland or Iceland. Detailed comparisons 

 would be a work in itself and is out of the question until identifica- 

 tions are complete, but a few are of interest. 



Because of less variation in ecological factors, there is little doubt 

 that the region of Point Barrow supports a fewer number of species 



