36 J. H. OETON. 



THE FUNCTION OF THE GLAND AND ITS CILIATED TRACT 

 IN THE BRANCHIAL OPENINGS OF AMPHIOXUS AND 



ASCIDIANS. 



In the anterior region of these animals there are also similar organs 

 which have doubtless a similar function, and a function in connexion 

 with the mode of feeding. These organs are a gland, and a ciliated tract 

 connecting the gland with the pharynx, namely, the sensory pit or 

 Hatchek's pit, and the Wheel Organ in Amphioxus, and the neural gland 

 and the dorsal tubercle in Ascidians. It has been suggested by V. Wijhe 

 (7, p. 121) and Andrews (14, p. 227) for Amphioxus, and by Herdman 

 (10, p. 52), Hartmeyer (11, p. 303), and Seeliger and Neumann (12, p. 61) 

 for Ascidians, that this gland may have the function of secreting mucus 

 which is passed on to the pharynx by the ciliated tract. The observations 

 here made on these groups of animals support these views. The gland 

 probably merely secretes mucus Avhich is passed on to the food-grooves 

 by the ciliated tract to serve for entrapping or embedding food-particles 

 and rendering the transportation of these easier than it otherwise would 

 be. Thus it is not improbable that the great variations observed in the 

 openings of the dorsal tubercle of Ascidians may be a means of distributing 

 mucus in various ways to the pharynx in correlation with minor differences 

 of food-collection on the pharynx ; such differences as may be due to the 

 well-known differences in structure of the pharynx. 



From the occurrence of sensory cells in Hatchek's pit in Amphioxus it 

 would seem that this organ is also in some way sensory, as V. Wijhe 

 (7, p. 120) has pointed out. In the light of the present researches it is 

 suggested that possibly this sensory pit may govern in some way the 

 supply of mucus from the gland itself and the endostyle, for the capture 

 ■of food-particles depends to a great extent on the amount of mucus 

 passing over the pharynx. Thus when a large amount of food-particles 

 is passing into the pharynx — as might be first appreciated by the 

 sensory cells in Hatchek's pit — a large amount of mucus would be 

 required to capture the food-particles. It is therefore not improbable 

 that the supply of mucus may be regulated by means of this sensory pit. 

 Whether any similar function is exercised by the neural gland in Ascidians 

 is perhaps more doubtful, but both Herdman (10, p. 52-3) and Seeliger 

 and Hartmeyer (11, p. 303) suggest that the dorsal tubercle in these 

 animals may have a sensory function. It may also be pointed out here 

 that if the neural gland in Ascidians is an organ for secreting mucus 

 which is passed on to the pharynx by the cilia in the dorsal tubercle ^ 



