GEROULD: CAUDINA. 167 
and often contains one or two highly refractive extranuclear chro- 
matic bodies. 
The spheruliferous corpuscles, which are found in small numbers 
among the much more numerous blood corpuscles, are like those 
which have already been described in the account of the connec- 
tive-tissue layer of the integument. The brown corpuscles have been 
mentioned in connection with the wall of the intestine. They are to 
be regarded as a modification of the colorless corpuscles, and their 
color is probably due to waste products contained in them. 
It seems probable that the irregular non-living mass of brown 
spherules which sometimes nearly fills the lumen of the Polian vesicle 
is derived from the brown wandering cells. I regard it as an excretory 
product. The fact that the brown cells are found in a living condition 
in the Polian vesicle and the close resemblance in the size of the 
spherules of the living cell to those of the dead mass lead one, in the 
absence of any other probable explanation, to regard the latter as being 
derived from the brown amoeboid cells. The spherules of the dead 
mass have no affinity for eosin or carmine, and only an occasional one 
is stained by haematoxylin.! 
3. CIRCULATION OF FLUIDS IN THE TENTACLES. 
If asmall specimen of Caudina is thoroughly stupefied and observed 
alive in sea water under alow power of the compound microscope 
(Zeiss, obj. A., oc. 3), the course of the water-vascular fluids in the 
tentacles can be readily followed by means of the numerous red blood 
corpuscles. The stream runs anteriad along the axial side of the 
tentacle, probably from the radial canal, until it is divided into two 
streams, which run side by side, first into the axia/ finger-like pro- 
cesses of the tentacles and thence into the two peripheral processes 
(Plate 6, fig. 78); the two currents then unite and flow posteriad, 
probably into the ampulla and thence, it is probable, into the abaxial 
side of the radial vessel. The circulation is thus a sort of rotation, 
which reminds one of the protoplasmic movements in Nitella; each 
stream flows quite to the tip of the arial process, which generally 
points directly anteriad, turns sharply upon itself, and runs into the 
abaxial process, which is curved outward in such a way that the 
stream meets with the least possible resistance; here again the 
1Such a mass of brownish spherules I have found at the extremity of an oyariau 
tubule of Thyone and similar spherules in the body cavity of Caudina. 
