114 PROF. 8. J. HICKSON ON | Feb. 3, 
sufficient to show that the Zanzibar specimens should be described 
as belonging to a new species. 
They appear to be most closely related to the Australian 
species Ceratella fusca, but differ from it in one or two characters 
which Spencer and his predecessors regarded as of generic 
importance. 
The genus was defined by Spencer as follows :—Colony 
irregularly branching; more or less expanded in one plane; 
growing from a creeping base. Main stem flattened, branches 
rounded and beset with bracket-like hydrophores. 
In C. minima from Zanzibar the main stem is not flattened 
but perfectly cylindrical in form, and the hydrophores are so 
extremely reduced or rudimentary that they are little more than 
ridges on the proximal lips of the hydropores. The branching, 
moreover, appears to be strictly in one plane, and the terminal 
branches are much more slender and delicate than in the other 
species. Before passing on to the specific characters, the size of 
the specimens must be considered. 
The measurements are as follows :— 
Specimen A. Specimen B. Specimen C. 
mm. mm. mm. 
Height of the colony ......... 29 22 3D 
Maximum expanse of the 
branchesian eee creer 65 38 50 
Diameter of main stem..... : 1:2 0:75 1 
The colonies of Ceratella fusca are from 11 to 5 inches in 
height; the largest Specuems of C. procumbens described by Carter 
were 11 inches long by 5 inches broad, and of C. spinosa 44 inches 
long by 2 broad. The height of Chitina ericopsis is 14 inches, 
with a trunk (main stem) 1 inch in diameter. The size of 
Dehitella is not given by Gray, but from the figures it may be 
judged that it is larger than Ceratella fusca. From these figures 
it is clear that the Zanzibar specimens are much smaller than the 
average size of the adult colonies of the other species. Are they, 
therefore, to be regarded as young colonies or as the representa- 
tives of a dwarf species? If they are young colonies, it is quite 
possible that the main stem or trunk becomes somewhat compressed 
in the plane of branching as the colony grows; but the fact that 
all the three specimens obtained are of approximately the same 
size, suggests that they have reached or nearly reached their 
maximum growth. The dwarfing of the tropical species of a genus 
that is principally distributed in temperate waters is not without 
parallel in the group of Celenterata. The very rudimentary 
character of the hydrophores, however, cannot be explained by 
the suggestion of immaturity, and must be regarded as of specific 
importance. It is true that no gonophores have been discovered 
in the specimens, but it is quite probable that, as in other 
Ceelenterates of the tropics, their production is rapid and strictly 
seasonal, so that no argument can be deduced from this character, 
either for or against the theory of juvenility. 
The Colony.—The branching is not very profuse, and strictly 
