274 
SIDNEY F. HAEMER. 
ring round the foot-gland or sucker of the larva of both Pedi- 
cellina and Loxosoma. Sensory hairs have hen 
described in various species of Ectoprocta; Nitsche (4), for 
instance, has figured on the tentacles of Alcyonella fun- 
go sa, tactile hairs exactly like those of Loxosoma, and 
arranged singly or in groups of two or three. In the former 
case each hair, and in the latter each group of hairs, is no 
doubt borne on a sense-cell similar to those of Loxosoma. 
Sense organs, in external appearance resembling the pair 
described above in L. crassicauda, occur in Rhabdo- 
pleura 1 . Lankester has suggested the possible homology 
between these organs and the “osphradia” (Spengel’s olfactory 
organ) of the Mollusca. Although this homology is not 
impossible, the character of the tactile organs of L. crassi- 
cauda seems to indicate that the posterior sense organs are 
merely specialised sense-cells, exaggerated in size, and I there- 
fore regard it as probable that these organs in the Polyzoa 
have no homology with the osphradia of Mollusca. 
The only portion of the nervous system whose development 
I have followed in the bud is the ganglion (in Loxosoma). 
Although the share which is taken by the derivatives of the 
different germinal layers in the budding processes of this genus 
is still obscure, the ganglion may be definitely stated to origi- 
nate from ectoderm cells. It is, in fact, developed from 
the floor of the vestibular cavity, and this can only be regarded 
as ectodermic, whatever may be the origin of the alimentary 
canal. In a longitudinal section through a fairly-advanced bud 
(fig. 15) it is seen that a narrow slit-like diverticulum of the 
vestibule passes behind the epistome. This diverticulum, 
which remains in very much the same condition throughout 
life (see fig. 11), does not give rise in toto to the ganglion, which 
is merely formed by a differentiation of some of its ectodermic 
cells. Hatschek (14), in his account of the budding of Pe di- 
ce 11 in a, describes the development of the ganglion as a diver- 
1 These organs are on the posterior side, and are two in number ; their 
position, however, differs somewhat from that of the similar organs of L . 
crassicauda. 
