Miscellaneous. 483 



M. Giard, relying on experiments tried at Roscoff, by means of 

 carmine administered to living Synascidians, has contended that 

 deglutition takes place by the dorsal side, that is to say by the side 

 opposite to the endostyle. This naturalist believes that the appa- 

 ratus by the aid of which the act is performed is the series of dorsal 

 languettes or the organs which represent them. 



In ClavelUna in particular these languettes, which are merely 

 prolongations of the transverse bands of the left wall of the 

 branchial sac, form a portion of a helicoidal surface upon which the 

 food -particles glide until they gradually reach the stomach. 



i[. Giard sought to determine the point at which the secretion 

 of the mucus takes place whjch envelops the nutritive particles. 

 This substance cannot be formed along the spiral apparatus or the 

 dorsal canal, for this region is devoid of glands. M. Giard there- 

 fore wonders whether the mucous matter does not proceed from the 

 endostyle ; nevertheless he does not explain how, according to this 

 hypothesis, the mucus passes from the ventral surface to the opposite 

 side. 



On my part I have experimented upon living specimens of Clavel- 

 Una and Perophora. In order to observe the mode of deglutition 

 in these Ascidians it is sufficient, without having recourse to carmine, 

 to place the living animal in sea-water containing a very small 

 quantity of mud in suspension. 



By this means we find, as stated by M. Giard, that deglutition 

 takes place by the dorsal surface ; only we discover at the same time 

 that the alimentary cylinder neither coincides with the median line 

 nor with the series of helicoidal languettes. 



The very distinct track formed by the food-particles starts from 

 the dorsal cup and proceeds in a somewhat oblique direction from top 

 to bottom (I place the mouth at the top), at a slight distance from 

 and to the right of the dorsal raphe. 



By focusing the microscope accordingly, we observe in an indi- 

 vidual lying on its left side first the body-wall and the branchial 

 sac, then the nutritive cylinder, and beneath this the helicoidal 

 languettes situated beyond the raphe. 



This, then, is the way in which deglutition is eflPected: — 



On a level with the pori-ccsophageal nerve-ring there exists a 

 band of vibratile cilia which conduct the nutritive particles towards 

 an organ in the shape of a pit, which is ciliated and situated on the 

 dorsal side in the neighbourhood of the cerebral ganglion. This 

 pit secretes a large quantity of mucus, by which the food-particles 

 are agglutinated together to form a cord, which descends towards 

 the orifice of the stomach, folloAving the course indicated above. 

 The alimentary cylinder increases a little in diameter as it descends, 

 and finally enters the stomach, the yawning aperture of which lies 

 at the bottom of the respiratory sac. 



One of the functions of the vibratile pit therefore seems to me to 

 be established : it secretes the mucus by the aid of which the food- 

 particles are agglutinated into a cord, which is conducted by a 

 ciliated branchial band into the stomach. — Bidletin de la Societe 

 Philomathiqne de Paris, S'^"'*' eerie, t. iv. no. 1, 1892, pp. 35, 36. 



