14 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



The microscopic organisms which form the food of salpa are 

 gathered up and conveyed into the stomach by means of an apparatus 

 which has been described so frequently that only a very brief account of 

 it need be given, although its prominence during the development of 

 salpa demands some acquaintance with it in order to render the account 

 of the life-history intelligible. 



On the middle line of the ventral surface of the pharynx there is a 

 longitudinal furrow, Plate XLV, Fig. 5, D, bounded by two thickened 

 borders. This structure is the endostyle. It is shown at end in Plate IV, 

 Fig. 2, and in many of the other figures. In the adult some of the cells 

 of its walls are glandular, secreting an adhesive substance, while other 

 cells carry cilia, which are so placed as to slide the adhesive excretion 

 along the endostylic furrow to the anterior end of the body, where the 

 endostyle ends between two ciliated bands, c&, one of which lies on each 

 side of the inner surface of the pharynx just inside the mouth. Each 

 ciliated band consists of two parallel rows of cilia close together, and 

 by their activity the adhesive matter from the endostyle is drawn 

 upwards along the sides of the pharynx, in fine threads, which stick to 

 and entangle all the organisms which touch them as they are swept in 

 by the current of water which passes through the pharynx. 



The pharynx, Plate IV, Fig. 2, c, and the atrium, g'", are in free com- 

 munication with each other, as already noted, except 011 the middle line, 

 where they are separated from each other by the "gill," o. In a median 

 longitudinal section, like the one shown in Plate XXXV, the outline of 

 each chamber is well marked. In a young embryo the "gill" is nearly 

 horizontal, and the atrium is above the pharynx, but as the animal grows 

 up the "gill" becomes more and more inclined, until in the adult, Plate 

 IV, Fig. 2, its posterior end approaches the ventral side of the body, and 

 the pharynx and atrium lie end to end ; the former extending farthest 

 backwards on the ventral middle line, while the latter extends farthest 

 forwards on the dorsal middle line. On each side of the "gill" the two 

 chambers communicate with each other, and I have not been able to find 

 in the adult any indication whatever, in their side walls, of the line where 

 the one chamber ends and the other begins. In front of the ganglion, s, 

 the pharynx occupies the whole cavity, as does the atrium behind the 

 nucleus, nu, and the imaginary line where they meet is probably inclined, 

 like the "gill," so that the cavity of the pharynx diminishes in size as we 

 pass backwards, while the atrium increases at the same rate. In Salpa 

 costata, where the nucleus is a considerable distance in front of the atrial 

 aperture, the tubular portion of the atrium is very long. 



