50 $$ 42, 48, 
THE POLYPI. 
CHAPTER VIII. 
ORGANS OF SECRETION, 
§ 42. 
Nothing like urinary organs have yet been found in Polyps. Perhaps 
the borders of the mantles of the cellular Polyps should be regarded as 
organs of special secretion, since by them the increase and production of 
these cells take place.” 
CHAPTER IX. 
ORGANS OF GENERATION. 
§ 43. 
Polyps reproduce by gemmation, fissuration, and by eggs. 
1. Fissuration is comparatively rare; it takes place nearly always lon- 
gitudinally, and the division may or may not be complete. 
2. Gemmation is their most common mode of reproduction. The new 
individuals may be completely detached, or may remain connected with the 
parent corallum. 
a: In gemmation, complete separation of the young individual is, on 
the whole, rare. It is best known in Hydra, with which the buds 
always appear upon a certain part of the body, — that is, at its union with 
the foot.” A bud of this kind consists always of a simple fold of the wall 
of the stomach and the skin, so that the stomach of the young individual 
is in direct communication with that of the parent, and the chyme can pass 
freely from one to the other. When the foot of this new being has acquired 
a proper development, it is completely detached at its inferior extrem- 
ity. 
6: Gemmation without separation of the new beings is quite common 
with Polyps, and occurs with very various modifications. The buds are 
formed sometimes upon the sides, sometimes upon the base of the body. 
In the first case, the coralla have a dendroid aspect; in the second, they 
are more lamelliform, spherical or lapidescent. These variations are not 
limited to certain genera or species, being often due to external influences, 
1 The calcareous tubes of Tubipora, and the 
corneous ones of the Sertularina and other Bryozoa, 
are, without doubt, secreted by the border of the 
amantle, as is true of the shells of mollusks. 
1 According to Roesel (Insektenbelust. III. p. 
504, 525. Taf. LXXXIII. fig. 3), fissuration takes 
place transversely with Hydra. Longitudinal 
fissuration is principally observed with the Madre- 
porina. When it is complete the cells of the coral- 
lum are definitely limited, as in Astraea, Favia, 
and Caryophyllia ; but, when incomplete, the cells 
are branched, lobulated, and of irregular contour, 
es in Agaricia, Macandrina, and Monticularia, 
Cc. . 
“2. Roesel (loc. cit. IMI. Taf. LXXXV. fig. 2, 3, 5, 
Taf. LXXXVI. and LXXXVIII. fig. g. h. and Taf. 
LXXXIX. fig. 4). The exceptions to this rue, 
which are sometimes observed, are probably due 
to lesions of an accidental nature. 
