Ctenophora. Echinoderms. 63 



Siphonoplior.'i, are nearly all voracious robbers; often swallowing- animals, 

 which one would suppose might easily overcome them. Inside the cavity 

 of Bcroe or in the pendant stalk of a Medusa are often seen small fish 

 which the apparently delicate organism dissolves and digests. 



In the bay of Naples the following Ctenophora occur: the barrel- 

 shaped, comparatively .toug-h Beroe (Fig. 85); the much more delicate 

 Callianira (Fig-. 87); Eueharis (Fig-. 86) consisting chiefly of water; and 

 lastly the curious Venus's Girdle, CestUS Veneris (Fig. 88). All of these 

 attract the attention of the observer by the beads of light which seem 

 to run over the body in various directions, displaying- all the colours of 

 the rainbow. This curious play of colours is caused by innumerable 

 little plates, which are placed in vertical rows one above the other, and 

 are moved up and down with great rapidity. By them the rays of light 

 are reflected in such a w^ay that the colours of the rainbow, which make 

 up white light, appear separately. These plates, arranged in rows like 

 the teeth of a comb, have caused these organisms to be called Cteno- 

 phora (« comb-bearers »). 



ECHINODERMS. 



This group of animals comprises the Sea-urchins, Sea-stars, Sea- 

 cucumbers, and Feather-stars. They are especially interesting to those 

 not acquainted with marine life, for no member of the group occurs 

 either in fresh water or on land. But the Echinoderms differ from most 

 terrestrial and freshwater animals in a turther way. If the lay mind be 

 rather doubtful as to details of anatomical structure, it knows that, for 

 example, birds, fishes and insects pos.sess a head ; that they are provid- 

 ed with wings, fins or legs. They have a moutli, and eyes, and many 

 other org-ans with which we are all familiar from every day observa- 

 tion : but how^ should he recognize these in a sea-urchin or in a star- 

 fish? These animals live, therefore they miist eat; but where is their 

 mouth? where are the limbs with which they grasp their prey ? They 

 live in the sea, but how do tiiey move about? Do they craul? Can they 

 see and hear? 



First of all it must be remembered that Corals and Medusae, for 

 instance, can do very well without head and tail, arms and legs, fins or 

 wings, and so can the Echinoderms. Still, the latter have a much more 

 complex structure than the former. Even their outward form is most 

 variable. Some are almost spherical (Fig. 7), others are flat like a 

 leaf (PalmijH's, p. 5), others again star-shaped (Fig. 1 and 3) ; some 

 are cylindrical, something like a cucuml)er in shape (Fig. 10); and lastly 

 some have the form of a flower attached by a short stalk, and seem to 

 possess sepals and petals (Fig. 5). The skin of these animals contains 

 a large number of diflerent but regularly arranged calcareous plates. In 



lapse immediately they are haiuileJ the least roughly, and can therefore not he taken 

 out (if the water, 'fhoy only live a few days in the Aquarium, although they are placed 

 separately in large glass cylindeis and seem to flourish very well for a time. — Most pe- 

 lagic animals shiiie at night, some with a '-ery strong light, and contribute laigely 

 to the Phosphorescence so frequently observed at sea. 



