THE LASSO-THROWERS. 57 
all together, each enclosed in a cup made of a pecu- 
liar substance called chitin, which is nearly allied to 
horn, and which also forms the skin of insects. The 
whole stem is only one individual, for a fine living 
thread passes down through the bottom of each cup 
and meets all the others within the stem, so that the 
food digested in each tiny stomach goes to feed the 
whole animal. 
Here then we have hundreds of tiny lasso-throwers 
acting as mouths and stomachs to one Sertularia, as 
this specimen is called. Each mouth or polypite is 
so small as scarcely to be seen even as a speck by 
the naked eye, yet it has sixteen tiny arms, and each 
arm is crowded with lasso-cells ! 
And now in the summer months, between May 
and September, small round bags (S, 2, Fig. 2 1) appear 
scattered along the branches of this animal-tree, and 
each one of these is full of eggs ; and by and by, when 
the eggs are hatched, young sertularians swim out as 
little round jelly bodies, and settling down on some 
stone or seaweed grow up into new stems of lasso- 
throwers. 
It is scarcely possible to conceive the number of 
minute beings which are feeding in this way at the 
bottom of the sea. This particular sertularia or sea- 
oak coralline (Fig. 21) covers the seaweed of our 
coasts with miniature animal forests, and yet it is 
one of the smaller kinds, sometimes not more than 
half-an-inch high. Others grow on shells forming a 
fleecy covering which looks only like a little white 
moss, but which is really a group of living animals. 
Every child must be familiar with a kind of rough 
crust frequently to be seen outside old shells, but pro- 
