420 
MOLL USCOLDEA. 
found attached to the wall of the chamber, the upper ( o ) yielding eggs, while 
within the lower ( t ) the male elements develop. Moss-animals are therefore her¬ 
maphrodite, the fertilisation of the eggs being effected by the two elements ming¬ 
ling freely together in the body-fluid. In all 
essential points, the above description would 
apply to any one of the seventeen hundred 
species, fossil and extant, which are known. 
Among the larger colonies may be 
mentioned certain fresh-water genera, found 
attached to the roots and branches of 
water-plants, which may form considerable 
masses; but these stocks are dull in colour 
and very inconspicuous, the beauty of the 
minute individual animals themselves being 
invisible to the naked eye. Some fairly- 
sized forms occur also among the marine 
genera, which are often marked by the 
great variety and beauty of their stocks. 
Many of these are delicate branching or 
tree-like growths some inches in height; 
take, for instance, the sea-mats ( Flustra ), 
or again, the still larger and more beautiful 
lace-corals, Neptune’s sleeves, such as are 
shown on p. 421, which, in spite of their 
name, are not true corals but bryozoans. 
The figured lace-coral ( Retepora ) is found 
in the nets used on the shores of the Atlantic 
Ocean and Mediterranean Sea. When 
fresh, the stocks—which resemble a fine, 
cup-shaped, or folded and frilled piece of 
lace—seem to be covered by a reddish 
organic mass, out of which arise the delicate 
tentacular crowns of the individual animals. 
These are, however, too small to be seen, 
except with a magnifying glass. When the 
soft-parts are removed, the stock is of 
dazzling whiteness, consisting chiefly of the chalky substance which binds the 
separate individuals together into a colony. Between the open meshes of the 
lace-work, multitudes of minute apertures are to be seen, which are the openings 
of the individual chambers or cells containing the bodies of the animals, and 
into which they can withdraw their tentacular crown as above explained. Another 
lace-coral from the Mediterranean is shown on p. 422. It rests upon a branched 
structure, a common calcareous alga which grows on a stone. The individuals of 
this genus ( Lcpralia ) are arranged in rows, and are further distinguished from 
Retepora and other moss-animals by the fact that the animals occur only on one 
side of the stock. We mention these lace-corals because of their being com- 
SECTION OF AN INDIVIDUAL OF Paludicellu 
(highly magnified). 
