PREFACE. 



The sessile barnacles are one of the dominant groups of littoral 

 animals. In vast profusion of individuals tliey inhabit the zone 

 between high-water mark and the liundred-fathom line. Their free 

 nauplii form an appreciable part of the food available for bivalve 

 mollusks and other animals subsisting on the plankton. The adult 

 barnacles, together with mollusks, are part of the food of bottom- 

 feeding fishes. In Japan barnacles are extensively utilized for fer- 

 tilizer, as fish and Limulus are with us. On the other side of the 

 account, it may be mentioned that barnacles are most widely laiown 

 as the chief organisms folding ships' bottoms. 



Although barnacles offer a wide field for systematic and ecological 

 study, they have been neglected by American naturalists. In the 

 early days of zoology they were classed with the mollusks, and were 

 collected by conchologists. After the group was transferred to the 

 Crustacea, conchologists lost interest, and but few students of 

 Crustacea took it up. Fortunately the Cirripedes found a historian 

 in Charles Darwin. His Monograph on the Subclass Cirripedia is 

 one of the most brilliant morphologo-systematic studies to be found 

 in the whole field of systematic zoological literature. In recent 

 years the works of P. P. C. Hoek and A. Gruvel, inspired by the high 

 ideals of Darwin, have stimulated renewed research, and a substan- 

 tial advance in our knowledge of barnacles must result from the 

 work of zoologists and paleontologists who have taken up the group 

 in England, Germany, Italy, India, and New Zealand. 



In America there is opportunity for systematic and faunistic work 

 on the southern and Pacific coasts especially, while the entire sea- 

 board abounds in cirripede material for the investigator of the prob- 

 lems of ecology and evolution. 



H. A. PlLSBRY. 



Philadelphia, May 1, 1916. 



