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RICHAED ASSHETON. 
quite likely that the vacuoles burst eventually and discharge 
the contained excretory granules into the rectum. I have not 
observed such a discharge of a vacuole in a living specimen, 
noram I prepared to say that the ruptured vesicles seen in 
sections are not due to artificial causes, but the whole appear- 
ance of the epithelium strongly supports the view put forward 
above. Harmer, in his paper on the excretory processes in 
ectoproctous Polyzoa, describes the excretion of granules 
containing artificial pigment from various parts of the ali- 
mentary canal thus (p. 154): “This process takes place by 
the separation of small round vesicles from some part of the 
wall of the alimentary canal, and probably from the caecum. 
These vesicles contain granules of Bismai’ck-brown, and may 
be seen in the stomach, intestine, or rectum, where they are 
no doubt on their way to the exterior.” Then, again, in dis- 
cussing, on p. 162, the nature of the natural colouring matter 
of the “ liver ” part of the alimentary canal he writes : “ With- 
out going into the question of the excretory value of the 
processes which take ])lace in the vertebrate liver ... I 
may express my conviction that this appearance of pigments 
like indigo carmine, carminate of ammonium, and Bismarck- 
brown in the granules of the walls of the alimentary canal in 
Polyzoa, taken in conjunction with the normal appearance in 
the same place of a natural pigment and the ultimate passage 
of much of that pigment into the brown body, is to be regarded 
as, in part at least, a process of excretion.” 1 would suggest 
that L. saltans indicates that the function of excretion, so 
far as the alimentary canal is concerned, is concentrated in 
the expanded terminal part of the intestine, and that the 
yellow pigment of the liver diverticula is of a different nature. 
'The cells of the rectum which produce the excretory pigment 
have an utterly different character to those of the liver 
diverticula. In fig. 22 the former, and in fig. 24 the latter 
type of cell may be seen. In the rectal excretory cell the 
nuclei are deep down and horizontally placed, as so often 
occurs in the secretory cells, and the granules appear to be 
forming near the nucleus and passing outwards towards the 
