36 



VERTEBRATE ZOOLOGY 



primitive, in that it has such a very large number of pharj igeal clefts. 

 In other respects Amphioxus may be accepted as an approximate 

 prototype of the ancestral chordate. 



SESSILE LIFE AND METHOD OF FEEDING OF AMPHIOXUS 



Along the sandy shores of the Mediterranean and other temperate 

 seas the "lancelet" leads a semi-sedentary life, burrowing rapidly 



FIG. 9. A group of lancelets (Amphioxus lanceolatus} in normal habitat, some 

 in the sedentary position with only the anterior end protruding from the sand 

 burrow, one in the foreground beginning to dig a new burrow, and others swim- 

 ming about in fish-like fashion. (Redrawn from indistinct photograph after 

 Wffley.) 



head first in the sand, leaving the head end protruding (Fig. 9) with 

 its oral hood and buccal tentacles outspread to test and draw in the 

 "sea-soup," as the food-laden water has been called. From time to 

 time the burrow is left and another made. The method of food gather- 

 ing is essentially that of a sedentary organism. There is no active 

 searching for food, but the water which is swept in quantities through 

 the pharynx and down through the pharyngeal clefts gives up its mi- 



