PHARYNGEAL GLAND-CELLS OF EARTHWORMS. 
273 
most parts ; and then the chromophil cells themselves form the 
limit of the mass. 
The smaller masses of chromophil cells, which occur in 
some abundance in this species in several segments behind 
the main mass, show interesting relations and give consider- 
able help in elucidating the origin of the tissue. 
Relation of Chromophil Cells to Septa. — The small 
masses of cells on septum 9/10 are directly in contact with 
the muscular fibres of the septum, taking the place of the 
peritoneum at the spots where they occur. At one point a 
still smaller aggregation appears to be essentially a slight 
swelling of the peritoneal covering of the septum. Again 
at another point a single cell of the chromophil type takes its 
place in the series of peritoneal cells with flattened nuclei on 
the septum. One of the larger aggregates is continuous 
through the septum with a smaller mass on the other side. 
The aggregates, of all sizes, are continuous with the peri- 
toneum. 
Relation to the Alimentary Canal . — The cells which 
lie on the alimentary wall in segment IX are situated imme- 
diately outside the muscular layer. Others are in close 
contact with the blood-vessels which occur external to the 
muscular- layer on the surface of the oesophagus, and not 
only on the outer side of the vessels, but also between the 
vessels and muscular fibres of the alimentary wall. In 
places where the muscular layer of the wall is not visible 
(probably because of gaps in the arrangement of the fibres), 
the cells are in actual contact with the epithelium of the 
oesophagus. Occasional cells are found singly here and 
there internal to the muscular layer, in the irregular space 
between the muscle fibres and the base of the epithelial 
layer. 
Relations to Blood-vessels. — The cells which are 
situated on the lateral oesophageal trunks are in direct 
apposition with the muscular or connective tissue coat of the 
vessels, which they surround on all sides. There is no 
separate peritoneal coat surrounding the vessel apart from 
