PHARYNGEAL GLAND OF THE EARTHWORM 55 
(b) Yellow cells of the alimentary canal. 
In the wall of the alimentary canal of the earthworm, between 
the epithelial cells, there are often found special cells filled with 
yellow spherules. These cells vary im size and shape; they 
may be either spherical or oblong, or even irregular and amoe- 
boid. The number of nuclei depends upon the size of the cell, 
and the cells oceupy a variable position in the wall of the gut, 
being either very deeply placed in the epithelium, near the 
coelomic cavity, or extending themselves to the lumen of the 
gut. Cuénot, to whom we owe a very good description of these 
cells, considered them as belonging to the intestinal epithelium, 
and ascribed to them an excretory function. According to 
Willem and Minne these cells do not belong to the alimentary 
canal, but are amoebocytes which originate from the haematic 
system. 
They make their way through the walls of the blood-vessels 
and the epithelial cells of the mid-gut, which they destroy on 
their way, and then, filled with the products of excretion, they 
leave the organism by way of the intestine. 
The distribution of these cells in different specimens is very 
irregular ; in some specimens they are rare and difficult to 
find, while in others they are very numerous. 
Up to the present these cells have only been mentioned as 
occurring in the wall of the alimentary canal between the crop 
and anus. During this study I frequently found them in the 
pharyngeal bulb and especially in the wall of the oesophagus, 
which they traverse in the same manner as they do the wall of 
the intestine. Text-figure 6, B and OC, shows these cells 
lying in the wall of the oesophagus, their protoplasm being filled 
with corpuscles of excretion, fat spherules, and some albuminoid 
bodies. Onseveral occasions I found the cuticle of the oesopha- 
sus perforated at the place of contact of the yellow cells, 
thus establishing a communication (Text-fig. 6, C, 0.) between 
that the bacteroid bodies are the real bacilli. Throughout his work Cuénot 
criticized this opinion, and described and figured these bodies as ‘cristal- 
loides’ of excretion. 
