442 THE ANNELIDA POLYCHAETA. 



The pharynx is short, with its dorsal portion alone ordinarily protrusible 

 and carrying forward the tentacles when extruded. The pharynx is followed 

 by a short oesophagus, a voluminous stomach, occupying most of the thorax 

 and narrowing caudad, and an intestine. At the anterior end of the stomach 

 there may be present two short lobes ordinarily reddish or yellowish in color, 

 while in some there is a highly peculiar internal caecum filling much of the cavity 

 of the stomach. 



The ampharetids are very sedentary in habit, living in tubes which they 

 neither leave nor move about. The walls of these tubes are normally composed 

 of fine mud over a lining membrane that is thin but usually tough. The tubes 

 are commonly buried in a vertical position in the mud of the bottom frequented 

 by the animals. The ampharetids that have been observed live upon such 

 small forms as species of Diatomaceae, Foraminifera, Globigerinae and other 

 Protozoa, microscopic Algae and algal spores. In securing such forms Ampha- 

 rete gruhei, for example, thrusts its anterior region from the mouth of its tube, at 

 the same time extruding its tentacles and sweeping them about over the adjacent 

 surface. Through the action of the tentacles and the ciha upon them small 

 balls of material are rolled up mixed with some mucus, these balls being passed 

 into the mouth and, when sufficient has been accumulated, are swallowed.^ 

 The alimentary canal of various species when opened is found to contain com- 

 monly fine mud mixed with the spicules of sponges, frustules of diatoms, shells 

 of Foraminifera, sometimes the setae of annehds, etc. 



The ampharetids are more or less limited to comparatively cold water, for 

 which reason they are rare in collections from the littoral zone of tropical regions 

 but abound in the Arctic, Subarctic, and Antarctic regions and in other regions, 

 at the lower depths in the ocean. Of the fifteen species of this family secured 

 during the explorations of the Challenger, ten were dredged at depths of 

 from 1,100 to 2,700 fms; and, of the nine species recorded below, three were 

 secured at depths below 2,200 fms. and none came from above the 493 fm. 

 level. 



Key to the Subfamilies and Genera. 



a. Paleae present A^npharetinae. 



b. Capillary setae present to the caudal end of the body Olanes Kinberg. 



66. Capillary setae confined to the anterior, or thoracic, region, 

 c. Fourteen somites l)caring capillary setae; tentacles ciliated. 



d. With three pairs of branchiae; paleae and chaetopods lacking on third segment. 



Neosabellides Hessle. 



' Cf. I'auvel, Rcchcrchcs sur les ampharetiens, Bull, sci., 1897, 30, p. 373. 



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