Physiology of Sagitta bipunctata. -295 



of the animal, with a soft, translucid, apparently mucous sub- 

 stance, which is coagulated and rendered flocculent by the addition 

 of alcohol ; it contains no other organs than the stomachal swell- 

 ing and the ovaries ; it is isolated, as well from the head as from 

 the tail, by transversal partitions. 



The stomachal swelling is a somewhat considerable canal, which 

 extends through the whole length of the cavity of the trunk ; it is 

 a little compressed laterally, but its width is throughout the same. 

 After having reached the last transversal partition, itthere describes 

 a small curve, taking a direction toward the anus, and during this 

 short passage it becomes funnel-shaped. It is difficult to detect 

 the structure of its walls, and what I shall here advance must not be 

 regarded as proved. These walls appear to be composed of three 

 layers. The outer one is formed of excessively minute annular 

 fibres, close together, and readily detected under a high mag- 

 nifying power. I have only been able to distinguish longitudinal 

 fibres in two limited spots, that is to say, only on the central line 

 of the walls. They form, in fact, upon the upper central line, as 

 well as on the lower line, two filaments isolated from one another 

 throughout the extent of the stomachal swelling, and are placed 

 exteriorly to the annular fibres. The central layer is formed of 

 polygonal cellular spaces, above or beneath which is perceived a 

 number of round bodies, produced by the union of very small 

 and nowise polygonal cellules. These are apparently glands, 

 which, perhaps, are destined to secrete the liquid necessary for 

 digestion. The internal layer is a homogeneous epithelium, 

 furnished with long and thin cilia possessed of a lively vibratory 

 motion. Above, the stomachal swelling is attached by a simple 

 ligament, tolerably resisting, extending throughout its length, to 

 the upper wall of the cavity of the trunk ; inferiorly, numerous 

 slender fibrous filaments are perceived, mostly ramified, attached 

 to the wall opposite to the cavity of the trunk, and which are 

 fixed to the stomachal swelling, on the other side of the superior 

 ligament. I have often taken these last for vessels. On this 

 point, as I shall not return to it, I may observe that I have never 

 been able to distinguish the least trace of a vascular system. The 

 observation of very young individuals, under a convenient mag- 

 nifying power, has furnished me with no result in this respect, 

 any more than the dissection of larger individuals ; but I do not 

 intend by this to affirm that there is a complete absence of the 

 vascular system. 



Most frequently the stomachal swelling is found in a state ap- 

 parently quite empty ; I have only observed it to be filled with 

 solid nutritive matter, such as fragments of small fishes and Crus- 

 tacea, in a few instances. When several of these animals were 



