OR FRESH WATER POLYZOA. 133 
nulus (plate 4, figs. 2 & 4,w’),and in others, for example 
in Pectinatella (plate 4), may have the edge of the ring 
ornamented with delicate spines furnished with hooks. 
Late in autumn the Polyzodén dies, and the statoblasts 
are set free to float during the long winter, the sensitive 
germ within being protected from the frost only by their 
tough coatings. They retain their vitality, however, 
until the warmth of returning spring awakens their sus- 
pended powers of growth. The young Polyzoén then 
increases in bulk, until it splits the sheath apart, and 
protrudes beyond the edges. The organs are well ad- 
vanced when this takes place, and the tube has already 
acquired its adult habit of retracting the plumes upon the 
slightest provocation. Its youth is a sunny holiday passed 
inthe open water, where it swims freely by the aid of cilia, 
which clothe the outer surface, but the sides of the stato- 
blast are finally separated so widely, that they drop off, 
and the wanderer seeks a resting-place under some old 
log or stone. Here a little gelatine, which subsequently 
becomes the tough, brown envelope (plate 3, D), fast- 
ens it to the surface, and henceforth its fate is insepara- 
bly linked to that of an inanimate mass. When securely 
ea eam ones hila still free, a little bulb 
: n is ernable -This was primarily a tiny, saclike 
ao... y AN 
ne parent cell, close to the bases of the muscles of the fold 
plate l; fig. 5, Y). The throat and stomach are derived 
from the transverse division of the minute sac into two 
portions, but it remains to be ascertained whether the 
intestine is made by an after-growth from the stomach, or 
by the division lengthwise of the throat. The tentacles 
