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 contaims 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 1s 
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 m 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 hquid 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 resistmg, 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- 
nifymg 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 
