448 
EDITH M. MUSGEAVE. 
are moved both towards the naked stem and towards the 
pinnated stem ; sometimes they are drawn in very much to 
the belly, a little after they are inclined to the back.” 
I regret that I can produce no evidence in support of this 
statement. The movement of the leaves was observed in all 
cases to be extremely slight, and extended over a consider- 
able interval of time. In many cases it was only after several 
hours that the leaves became slightly inclined veiitrally 
or dorsally upwards or downwards, but the change in posi- 
tion was invariably accompanied by a change in their contour, 
and seemed to be entirely dependent upon the state of hydro- 
static dilatation or otherwise of the colony. 
Upon internal examination of the rachis, the tissue around 
the insertion of the leaves was observed to be composed almost 
entirely of that distensible spongy tissue which we have reason 
to suppose plays no unimportant part in the dilatations and 
contractions of the colony (pp. 463-464). In this region the 
musculature is extremely feebly developed, and serves chiefly 
for the protraction and retraction of the autozooids, the 
coelenteric cavities of which are separated from the large 
canals of the rachis merely by a thin connective-tissue layer. 
The arrangement of the musculature in connection with the 
spongy tissue and controlled movements of the colony is 
further discussed on pp. 460-473. 
The Canal System. 
As very excellent accounts already exist of the form, 
arrangement, and general anatomy of the canal system of 
Pennatulids it is necessary to add little to what has already 
been published on this portion of the subject. 
For the earliest account we are indebted to Kolliker (1880), 
who described most carefully and thoroughly the arrange- 
ment and general anatomy of the canal systems in several 
genera: Pen na tula, Pteroeides, Virgularia, etc. He 
also states that, with the exception of the presence of the 
four large central canals in Pennatulids, the canal system 
