256 Dr. R. von Lendenfeld on Guara-Polyps 
cells, and perhaps also sense-cells. This part of the guard- 
animal, the muscular stem being deficient, 1s not very mobile, 
and it is protruded only for a short distance from the terminal 
orifice of the nematophore. In the basal part of the nemato- 
phore there is a second head, which exactly resembles an ad- 
hesive polyp; its thickened extremity can be protruded far 
out of the inferior aperture of the nematophore, and it pos- 
sesses an endodermal axis. 
Although at the first glance the whole rather gives us the 
impression that we have to do here with two modified polyps, 
the simple undivided endodermal axis indicates that the whole 
is homologous with a single polyp. If we trace the develop- 
ment of these guard-animals we see distinctly that both pieces 
are parts of an originally simple armed polyp. ‘Thus the end 
of the branch always forms a pair of guard-polyps; long 
before the nutritive animals in front of hese have fecout da 
veloped, the next pair of machopolyps sprouts. At the ends 
of the branches of young stocks we can find all stages ; and in 
this way it is easy to trace the development. 
Young guard-polyps of this kind are inserted in chitinous 
calices, ie hinder margin of which is somewhat higher than 
the Bicnor margin ; ‘they are completely filled with urti- 
cating capsules oad tolerably mobile, so that they can stretch 
forth ane mitrailleuse-like heads Os a considerable distance. 
While no chitine is secreted at the anterior side, the hinder 
margin grows very rapidly. In this way the nematophore ac- 
quires ie form of a very obliquely truncated straight circular 
cylinder. ‘Then the chitine secretion ceases at ans lower part 
of the elliptical margin, while the uppermost part grows in all 
(o) 
directions, and its eAareine finally unite again into a tube, 
This tube then elongates, and in some Aglaophenice bends 
outwards in a hook-like form. 
In some instances the formation of two apertures is not 
attained; and then the nematophores possess a wider or nar- 
rower cleft, which unites the two apertures. ‘This applies 
without exception (?) to those nematophores which are closely 
applied to the upper surface of the nutritive animal in the 
plane of symmetry of the branch, the unpaired, superior macho- 
polyps. 
Even when the two apertures are separ ated, when a nutri- 
tive polyp is mm course of formation in fan of the nemato- 
phore, and the buds of the next pair of guard-animals are 
already indicated, no adhesive cells are yet to be met, with; 
there is rather a urticating Meg behind each aperture. 
It is only subsequently that small drops begin to appear in 
the supporting cells between the oneness of the lower 
