Ctenophora. Echinoderms. 63 



Siphonophora, are nearly all voracious robbers; often swallowing animals, 

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

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

 which the apparently delicate organism dissolves and digests. 



The Neapolitan forms include the barrel-shaped, comparatively tough 

 Beroe (Fig. 86); the much more delicate form Callianira (Fig. 87); 

 Eucharis (Fig. 85) 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 rain- 

 bow. 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 way 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 Ctenophora 

 ("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 further way. If the lay mind be 

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

 example, birds, fishes and insects possess a head; that they are pro- 

 vided with wings, fins or legs. They have a mouth, and eyes, and many 

 other organs with which the least zoological of men is familiar from 

 every day observation; but how should he recognize these in a sea- 

 urchin or in a starfish? These animals live, therefore they must eat; 

 but where is their mouth? where are the limbs with which they grasp 

 their prey? They live in the sea, but how do they move about? Do 

 they crawl? 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 (PalmipeSj p. 5), others again star-shaped (Fig. 1 and 3); some 

 are cylindrical, something like a cucumber 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 different but regularly arranged calcareous plates. In 



can therefore not be taken out of the water. They only live a few days in the 

 Aquarium, although they are placed separately in large glass cylinders and seem 

 to nourish very well at 'the commencement. Most pelagic forms shine at nighl, 

 some with a very strong light, and contribute largely to the Phosphorescence 

 so frequently observed at sea. 



