EXPERIMENTAL OBSERVATIONS ON PENNATULIDS. 453 
“ Wheu tlie trunk is opened lengthways a saltish liquor 
flows out of it, so viscid as to hang down an inch.” 
The viscidity of the fluid contained in the canals was notice- 
able in all the specimens which came under my observation, 
and is, in my opinion, attributable to a mucoid secretion 
which exudes in considerable quantity from a profusion of 
gland-cells in the epithelial linings of the lai'ge canals (figs. 8 
and 9) of the stalk and rachis. In this viscid exudation from 
the deeply staining gland-cells particles of carmine were 
often observed. 
After an interval of a hundred and twenty years, during 
which period the zoological records are mute on this subject, 
Kolliker (1880) published a carefully compiled account of the 
canal systems of Pennatulids, but apparently makes no state- 
ment as to the nature of their fluid contents. Tlie canals, how- 
ever, he describes as “ nourishing canals,” so that doubtless he 
considered the probability of the presence of nutrient matter 
in the liquids contained in them. 
Later the brothers Marshall (1882, p. 33) made a statement 
to the effect that the fluid contained in the canal system of Pen- 
natulais probably nutritive but mixed largely with sea- water. 
After a comparative study of the arrangement and anatomy 
of the canal system of Pennatulids and other Alcyouaria 
(Alcyouium, Corallium, etc.) and their physiological 
beliaviour and condition when subjected to experiments with 
nutrient (Pratt, 1905) and non-nutrient substances, as in the 
experiment herewith recorded, we have strong evidence for 
believing the fluid contents of the canal system to be composed 
mainly of sea-water, in which nutrient matter may be dissolved 
or suspended in minute particles, and a mucoid secretion (fig. 
9) in which foreign particles, harmful or useless to the colony, 
may become embedded and carried to the exterior. 
II. 
A freshly captured specimen of Pen na tula rubra was 
placed, as in the former experiment, in a tank of running, 
filtered sea-water about 5 p.m., April 14th. By means of a 
