STUDIES IN MARINE ECOLOGY. 



183 



Pelecypoda Con't. 



Venus mercenaria . 



Yoldia limatula . . 

 Zirphaa crispata . 



Cephalopoda. 



Loligo pealii . 



S. 3 



Chordata. 



Appendicularia longicauda . , . 



Amarcecium constellation 



Amarcecium pellucidum 



Amarcecium stellatum 



Botryllus schlosseri 



Didemnum lutarium 



Dolichoglossus kowalevskyi . . . 



Molgula manhattensis 



Molgula papulosa 



Molgula arenata 



Perophora viridis 



Styela partita 



iv. 



The entire mass of data available was analyzed in 191 7 and 

 again in 1920 in an attempt to discover the relationships existing 

 between animal associations from the different types of environ- 

 ments. The first type of analysis was planned to discover the 

 number of species common to different combinations of these 

 habitats and conversely to find the number of animals peculiar 

 to each type of habitat. The analysis was not repeated after 

 the 1 92 1 records were available because it was not considered 

 that these records would materially change conclusions already 

 arrived at by the preceding work. 



The analysis of the records from 1915-1920 inclusive follows: 



