296 W. WOODLAND, 
width of the axis, as compared with the width of the spicule, 
is variable in different spicules, it being noticeably small, e. g, 
in the lancet-shaped or monaxon spicules (fig. 14). 
I have never observed any horny sheath enclosing the 
spicule, such as that, e. g. figured by von Koch in the case of 
the spicules of Clavularia prolifera, and since, up to the 
time when the spicule attains its maximum size, the whole 
surface-area of the spicule is having in a varying degree 
fresh calcareous matter deposited upon it by the investing 
protoplasmic layer, I am inclined to think it does not possess 
one—at least not one of any considerable thickness. 
With regard to the position of the nuclei on the more adult 
spicules, there is only one remark to make, and that is that 
in general one nucleus is to be found at one extremity of 
the “caudal vertebra” body of the spicule, and one on a 
process at the opposite end, but this position of the nuclei is 
not an absolutely constant one, and is probably of little or no 
significance. 
The intimate structure of the Aleyonarian spicule has been 
investigated by Bourne and others, and since I have nothing 
to add to their accounts, there is no need for me to here 
describe this. 
REMARKS ON THE Forms or ALCYONARIAN SPICULES. 
Like most, if not all, calcareous spicules which originate in 
connection with an isolated move or less spherical mass of 
protoplasm containing one nucleus—a single cell—the Alcyo- 
narian spicules at their first appearance are approximately 
spherical in form. Further, as is also universally the case, 
bi-division of the nucleus of this cell! containing the spherical 
sclerite is followed by an elongation of the spicule more or 
less in the direction of nuclear division. And, in Alcyo- 
nium at least, it is not difficult to see why this should 
be so, for the scleroblast resembling all other isolated cells 
1 Bi-division of the calcoplasm must also occur. 
