PHARYNGEAL GLAND-CELLS OF EARTHWORMS. 
269 
The Capsule. — A peritoneal covering limits the lobes 
in some places. The nuclei of this membrane are rounded or 
slig*htly flattened; the membrane itself is in places a distinct 
pink-staining (in hsematoxylin and eosin preparations) mod- 
erately thick expansion. In some regions, while it is still 
possible to speak of an investing membrane, the cells com- 
posing this latter are seen to be continuous with the chromophil 
cells and to have the same cytoplasmic constitution. In 
other places no investing membrane is present. 
In the adult Pheretima therefore, the chromophil cells 
form lobular aggregations covering the muscular mass of 
the dorsum of the pharynx ; and in some species they also 
extend backwards behind the pharynx as lobe-like masses. 
The cells also extend deeply inwards amongst the muscular 
fibres in the direction of the pharyngeal epithelium; but 
here they become modified, the cytoplasm being progressively 
converted into connective tissue. The connective tissue of 
this region has therefore probably a double origin. The 
descriptions of the peritoneal capsule suggest that it and the 
chromophil cells are modifications of the same tissue ; where 
the capsule is absent, the cells lining the coelomic cavity have 
become chromophil cells; where present, the cells in immediate 
relation to the cavity have become flattened, while those 
underneath have taken on the chromophil character. 
Lumbricid^;. 
As an example of what is seen in the dissection of one of 
the Lumbricidse, it will be sufficient to describe Helodrilus 
caliginosus, perhaps the commonest of all earthworms; 
the histological appearances in this species are similar in all 
main features to those of Pheretima (except that there are 
no “ blood-glands ” among the chromophil cells), and they 
therefore need not be detailed. Instead, an account of the 
microscopical structure of the chromophil tissue in Helo- 
drilus parvus will be given; this species is too small to 
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