APPENDIX. 389 
which keep the microscopically small and transparent nurse 
swimming about freely in the sea. This fringe of cilia is marked 
in Fig A 2—A 4, on Plate VII., by the narrow alternately light 
and dark seam. The nurse then, in the first place, forms a per- 
fectly simple intestinal canal for nutrition, mouth (0), stomach (7m) 
and anus (a). Later, the windings of the fringe of cilia become 
more complicated, and there arise arm-like processes (Fig. A 3— 
D8). In sea-stars (A 4) and sea-urchins (C4) these arm- 
like processes, which are fringed with cilia, afterwards become 
very long. But in the case of sea-lilies (B 3) and sea-cucumbers 
(D 4), instead of this, the fringe of cilia, which at first, through 
winding in and out, forms one closed ring, changes subsequently 
into a succession of separate ciliated girdles, one lying behind 
the other. 
In the interior of this curious nurse there then develops, by 
a non-sexual process of generation, namely, by the formation of 
internal buds or germ-buds (round about the stomach), the 
second generation of Star-fishes, which later on become sexually 
ripe. This second generation, which is represented on Plate 
IX. in a fully developed condition, exists originally as a stock 
or cormus of five worms, connected at one end in the form 
of a star, as is most clearly seen in the sea-stars, the most 
ancient and original form of the star-fishes. The second 
generation, which grows at the expense of the first, appropriates 
only the stomach and a small portion of the other organs of the 
latter, but forms for itself a new mouth and anus. The fringe of 
cilia, and the other parts of the body of the nurse, afterwards dis- 
appear. The second generation (A 5—D 5), is at first smaller or 
not much larger than the nurse, whereas, by growth, it afterwards 
becomes more than a hundred times, or even a thousand times, as 
large. If the ontogeny of the typical representatives of the 
four classes of Star-fishes be compared, it is easily seen that 
the original kind of development has been best preserved in 
sea-stars (A) and sea-urchins (() by inheritance, whereas’ in 
sea-lilies (B) and sea-cucumbers it has been suppressed accord- 
ing to the laws of abbreviated inheritance (vol. i. p. 212). 
