HABITS AND DISTRIBUTION. 9 



stomata, but, as Johannes Miiller put it, differed from them 

 to a greater extent than a fish differs from an Amphibian. 



HABITS AND DISTRIBUTION. 



In consequence of the extension of the firm, and at the 

 same time elastic, notochord to the tip of the snout, 

 Amphioxus possesses an extraordinary capacity for bur- 

 rowing in the sand of the sea-shore or sea-bottom. If an 

 individual be dropped from the hand on to a mound of 

 wet sand which has just been dredged out of the water, 

 it will burrow its way to the lowest depths of the sand- 

 hillock in the twinkling of an eye. 



The frontispiece is designed to illustrate the chief 

 positions in which Amphioxus may be observed. It is 

 represented swimming, lying on the sand, and buried in 

 the sand. 



Its usual modus vivcndi is to bury the whole of its 

 body in the sand, leaving only the mouth with the ex- 

 panded buccal cirri protruding. When obtained in this 

 position in a glass jar a constant inflowing current of 

 water in which food-particles are involved can be ob- 

 served in the neighbourhood of the upstanding mouths. 



The food consists almost entirely of microscopic plants 

 (Diatoms, Desmids, etc.) and vegetable debris. 



While passing through the pharynx the food becomes 

 involved in the slimy secretion of a gland at the base of 

 the pharynx known as the cndostyle or Jiypobrancliial 

 groove (cf. Figs. 2 and 3), and is thus held in the pharynx 

 while the water with virhich it entered flows out through 

 the gill-slits into the atrial chamber. The food is then 

 carried through the intestine enveloped in a continuous 

 cord of slime or mucus, which is kept in perpetual motion 



