THE CALCIFEROUS GLANDS OF EARTHWORMS. 
459 
This conclusion of Lang’s is supported by Freudweiler’s subsequent work in 
Enchytrseids (10), by Schiller’s on Arenicola (24), and by Sterling’s on Eisenia 
and Pheretima (28). It is challenged by Vejdovsky (30, 3 1 ), who goes to the 
extreme of viewing the sinus as contained within the entoderm. “ Choosing the 
Enchytrseidse as a starting-point, Vejdovsky shows that the peri-enteric sinus is 
crossed by thin protoplasmic strands passing between certain basal replacing cells 
of the intestinal epithelium, which bounds the sinus on its inner side, and a 
connective-tissue-like membrane which limits it externally ; intimately associated 
with this membrane are a number of flattened, hemispherical, or sometimes stalked 
cells, which project into the sinus. External to the membrane are the muscular 
coats of the intestine and the. chloragogen layer. The membrane (vasothel) is 
interpreted as having been separated from the intestinal epithelium ; the cells in 
connection with the vasothel as having migrated outwards from the layer of 
replacing cells ; and the strands which cross the cavity of the sinus as constituting 
evidence of the original unity of the outer with the inner wall of the sinus. The 
sinus is therefore contained within the entoderm.” (The quotation is from a former 
paper by one of us, 26.) 
Thus Lang and Vejdovsky (to quote again from the same paper) “ agree that 
the origin of the vascular system is to be sought in the accumulation of fluid at 
the base of the layer of intestinal epithelium, but thereafter they part company. 
Lang holds that the original position of the fluid is between epithelium and 
surrounding muscular layer ; Vejdovsky, that it is within the epithelial layer itself, 
since it is limited externally by the basement membrane of the epithelial cells and 
by certain, originally amoeboid, replacing entodermal cells which associate them- 
selves closely with the membrane.” Whether or not, therefore, we consider the 
occasiohiTliuclei on the outer side of the sinus as entodermal, and detached from 
the alimentary epithelium, there can be no doubt that the blood in the sinus 
directly bathes the base of the lining cell layer of the tube. 
The investigations on the alimentary sinus in the Annelida have naturally been 
carried out mainly or altogether in reference to the intestinal region, and we do 
not know of any definite statement as to how far forwards the sinus extends with 
the relations that have been described. According to our preparations, that portion 
of the alimentary tube with which the calcifer'ous glands are associated possesses 
in all cases a sinus with the relations described for the more posterior portion of 
the canal. 
On Rodlet Epithelium. 
The cells of the calciferous glands and of the neighbouring part of the alimentary 
tube have often been described as ciliated, and in some cases they undoubtedly are 
so. In other cases, however, there occurs on their free surface a layer of rodlets, 
which has apparently hitherto escaped recognition, or has been mistaken for cilia. 
We place here, therefore, a short general account of rodlet epithelium. 
