20 J. H. ORTON. 



misleading. It is to clear up our ideas on this matter that the present 

 account is written. 



It is generally stated that the current through the pharynx of Am- 

 phioxus is effected by the cilia on the gill-bars, and that the food-particles 

 are collected in the endostyle which conducts them forwards to the peri- 

 pharyngeal bands (1, 2, and 3). The latter are then described as conducting 

 the collected food to the dorsal groove, which in turn conducts it backwards 

 to the intestine. These statements are vague and wrong and misleading, 

 inasmuch as there are on the gill-bars at least two sets of cilia which 

 function in quite different ways, and the endostyle does not conduct food- 

 particles forwards, as will be seen from the following description : — 



MODE OF FEEDING IN AMPHIOXUS. 



^Vhile the animal is at rest a current of water is being taken in continu- 

 ously at the mouth and expelled at the atriopore. This current serves 

 for the nourishment of the animal, and doubtless is also a main factor in 

 its respiration. If an Amphioxus* be placed in water containing fine 

 particles of carmine in suspension or in water containing diatoms and 

 dissolved methylene blue, a mass of particles embedded in mucus very 

 soon collects in the dorsal groove of the pharynx and is passed on into the 

 intestine. The living animal after being fed in this manner has the 

 appearance indicated in Fig. 1. 



INGOING^ MRb. ^N. ^h. Fk At OUTGOING 



CURRENT CURRENT 



i'lG. l.f — View of a living Amphioxus shortly after being fed with carmine particles, to 

 show the collection of food in the dorsal groove and the intestine, and the course 

 of the main current through the body ( x about f ). 



r.M. Food masses in the dorsal groove of the pharynx and in the intestine. 

 M. Mouth, between which and the end of the arrow indicating the ingoing 



current is situated the buccal cavity. The outgoing current leaves the 



animal at the atriopore. 

 At. The Atrium, the space between the pharynx and the body wall through 



which the current passes after leaving the pharynx, Ph. 

 Ph. The pharynx or branchial sac. 

 En. The endostyle. 



P.b. The peri-pharyngeal band of the left side. 

 A. Anus. 



* The observations recorded in this paper were made on the species Branchiostoma 

 lanceolatum. The general similarity in structure of the species of this genus, however, 

 renders it higlily probable that the processes here described will apply to all the group. 



f I am indebted to Mrs. Orton for the drawing for this figure, and also for assistance 

 with Figures 6, 8, and 9. 



