172 University of California Piihlications in Zoology [Vol. 18 



to point to the conclusion that in Cambrian times the annelids had 

 entered all the life zones of the oceanic waters except possibly the 

 abyssal, and that the principal divisions of the annelids were clearly 

 established in pre-Cambrian times (Walcott, 1911; Osborn, 1917). 



The distribution of the annelids has received careful attention 

 only in recent years. Michael Sars (1850), one of the first investi- 

 gators of oceanic fauna, published the results of dredgings along the 

 coasts of Norway, including in his report the annelids collected. The 

 greatest depth to which his dredging extended, however, was only 

 300 fathoms. Claparede (1875) briefly described the annelids col- 

 lected by the "Lightning" Expedition from depths to 650 fathoms. 

 Ehlers' work (1875) on the distribution of Annelida, collected by the 

 "Porcupine" Expedition, is of greater importance because that was 

 the first expedition in which the bathymetric and horizontal distribu- 

 tion of the annelids was considered on a large scale. The work of 

 Darboux (1899) on Aphroditidae along the coasts of France and in 

 the Mediterranean Sea also adds to the knowledge of distribution of 

 that family of annelids. 



The greatest contribution to science in the studies of distribution 

 of marine life, however, was made by the "Challenger" Expedition 

 (1872-1876). This ship circumnavigated the globe, its dredging at 

 various latitudes extending to depths of over 4,000 fathoms. Animals 

 dredged were grouped and classified by a number of specialists belong- 

 ing to different nationalities. The lot in annelid studies fell to 

 Mcintosh, who rendered excellent service. In this country the United 

 States Survey Steamer "Blake" explored the Gulf of Mexico, the 

 coasts of Florida and the Caribbean Sea. The United States Steamer 

 "Albatross" has been engaged for a number of years in explorations 

 of the Atlantic coast and the Pacific Ocean. Our knowledge of anne- 

 lids in this country has been enlarged by the reports of E. Ehlers, 

 J. P. Moore and A. Treadwell. 



As a result of all these investigations the physical conditions of 

 the oceans are to some extent known, and enough has been learned 

 about the distribution of marine life so that questions as to how deep 

 and how far north or south it extends no longer occupy the minds 

 of biologists. It is known that life exists at all depths and in every 

 latitude. The question that is of interest to every biologist at the 

 present time is : "What is the influence of environment on animal life 

 in general, and wliy are certain kinds of animals limited to certain 

 . areas ? 



