Come and look at it.  It is a horny-branched stem with a double row of tiny cups all along each side.  Out of these cups there appear a row of tiny cups all along each side (see Fig. 5), Out of these cups there appear from time to time sixteen minute transparent tentacles as fine as spun glass, which wave about in the water.  If you shake the glass a little, in an instant each crystal star vanishes into its cup, to come out again a few minutes later; so that now here, now there, the delicate animal-flowers spread out on each side of the stem, and the tree is covered with moving beings.  These tentacles are feelers, which lash food into a mouth and stomach in each cup, where it is digested and passed, through a hole in the bottom, along a jelly thread which runs down the stem and joins all the mouths together.  In this way the food is distributed all over the tree, which is, in fact, one animal with many feeding-cups.  Some day I will show you one of these cups with the tentacles stretched out and mounted on a slide, so that you can examine a tentacle with a very strong magnifying power.  You will then see that it is dotted over with cells, in which are coiled fine threads.  The animal uses these threads to paralyze the creatures on which it feeds, for at the base of each thread there is a poison gland.

In the larger Sertularia the whole branched tree is connected by jelly threads, running through the stem, and all the thousands of mouths are spread out in the water.  One large form called Sertularia cupressina grows sometimes three feet high and bears as many as a hundred thousand cups, with living mouths, on its branches.

The next of my minute friends I can only show to the class in a diagram, but you will see it under the fourth microscope by and by.  I had great trouble in finding it yesterday, though I know its haunts upon the green weed, for it is so minute and transparent that even when the weed is in a trough a magnifying-glass will scarcely detect it.  And I must warn you that if you want to know any of the minute creatures we are studying, you must visit one place constantly.  You may in a casual way find many of them on seaweed, or in the damp ooze and mud, but it will be by chance only; to look for them with any certainty you must take trouble in making their acquaintance.

[Illustration:  FIG. 6. Thuricolla folliculata and Chilomonas amygdalum. (Saville Kent.)

1, Thuricolla erect. 2, Retracted. 3, Dividing. 4, Chilomonas amygdalum. hc, Horny carapace, cv, Contractile vesicle. v Closing valves.]