19 
annulated, generally distributed over the hydrocaulus ; 
hydranth with about twenty-four tentacles, alternately ele- 
vated and depressed in extension ; hydrothec rather wide, 
with even margin. 
Attached to buoys, Loch Long, Scotland. 
It is in the possession of the appendages destined for fissi- 
parous reproduction that the chief peculiarity of Schizo- 
cladium is to be found. These (figs. 2, a, b,c) are deve- 
loped in abundance from all parts of the hydrocaulus. They 
are in the form of cylindrical or slightly club-shaped ramuli, 
and commence just like the ordinary branchlets, as offshoots 
from the hydrocaulus, consisting, like these, of a continuation 
of the ceenosare invested by a chitinous perisarc, but dif- 
fering from them in a very important point by never carrying 
hydranths. Their ceenosare becomes somewhat thickened 
towards the distal extremity, where it is, as elsewhere, 
inyested by the perisarc, here very delicate and destitute of 
the annulation which exists on all the rest of the appendage. 
After the fissiparous branchlet has attained its complete 
length the contained ccenosarc still continues to elongate 
itself. In doing so it ruptures the delicate pellicle of chitine 
which closes the extremity of the branchlet, and extends 
itself quite naked into the surrounding water (fig. 2, 6). 
It is now that the process of fission commences. A con- 
striction takes place in the ceenosarc at some distance below 
its free extremity, and in the part still covered by the chitin- 
ous perisare (fig. 2,6). The constriction rapidly deepens, 
and ultimately cuts off a piece (fig. 2, c), which slips entirely 
out of the perisarcal tube, and becomes a free zooid (fig. 2, d), 
while the surface of disseveration soon heals over, and the 
axial cavity of the free frustule becomes here as completely 
closed as at the opposite end. 
The detached frustule is now about ;3; of an inch in 
length, with distinct endoderm and ectoderm, and strikingly 
resembles a planula in all points except in the total absence 
of vibratile cilia (fig. 3). It attaches itself by a mucous ex- 
cretion from its surface to the sides of the vessel, and exhibits 
slight and very sluggish changes of form. 
After a few hours it will be found that the mucous excre- 
tion has formed round the fission-frustule a tube of great 
tenuity and transparency. The frustule moves slowly along 
the sides of the vessel, and in doing so withdraws itself from 
the first-formed portion of its sheath, which now remains 
behind, adhering to the vessel as an extremely delicate 
tubular pellicle (fig. 4), while the frustule continues the 
excretion from its surface, thus reminding us of the mode in 
