300 W. WOODLAND. 
extension of the amphiccelous extremities of the spicule is not 
uniform; on the contrary, the “head” of the spicule, or 
rather rim, becomes divided into two, three, four, or more 
regions producing the large processes in every case observable 
(figs. 4, 5, and 7, and text-fig. C above). Any spicule at this 
stage seen sideways from any aspect will thus present the 
appearance of the ordinary “caudal vertebra,” with its 
concave-headed dumb-bell basis, and more or less well-deve- 
loped processes projecting from two, three, or alt of its four 
angles according to the number of these developed, and to 
the side of the spicule presented to observation. 
From the “ caudal vertebra” stage onwards, it apparently 
depends entirely on the influence of the heterogeneous con- 
stitution of the surrounding medium which of the angles or 
corners shall develop into the elongated branches proceeding 
from the main body or basis of the spicule, and which shall 
remain inconspicuous. In some cases indeed, the extremities 
of the dumb-bell elongate, but only very occasionally in 
deeply-situated spicules. Adjacent spicules and other struc- 
tures must exercise an influence on a developing spicule, and 
therefore determine to some extent at least its mode of growth, 
and seeing that the extreme irregularity of form found among 
the numerous spicules (“no two spicules in the field of the 
microscope are alike,’’? Hickson) is alone congruous with the 
view that such is related to the irregularity of the surround- 
ing conditions—different conditions necessarily obtaining in 
the case of each spicule—this view is doubtless the correct 
one. 
The alternative view that the furcations of the Alcyonium 
spicule are to be accounted for in the same manner as, e. g., 
the dichotomy of the lower Cryptogams, seems to me unlikely 
since, in this latter case, the branching is mostly related to 
food-supply—a large surface area being essential to the effi- 
cient nourishment of a large bulk—but in the case of the 
spicule the internal mass does not require nourishment and 
hence the increase of surface area of the cell-substance cannot 
be related to that end. I regard the cell-substance investing 
