60 Part second. 



heavy wooden beams, to which are attached pieces of old nets, untwisted 

 rope ends and other such material; the whole is dragged by means of a 

 strong rope over the bottom of the sea. The branching corals are entan- 

 gled in the nets and ropes, break off and are pulled up with them. To 

 use the corals, the bark with the polypes is brushed off and the 

 outermost layer of the skeleton filed away; afterwards it is ground with 

 emery-powder and oil, and finally polished with steel. The beads are tur- 

 ned and pierced on a lathe, figures are cut out with graving-tools. The 

 value of corals varies already greatly, even before they are worked. The 

 thicker roots are often perforated by boring animats (worms and sponges) 

 and fetch between 5 and 20 frs. per kilogramme. Good ordinary pieces 

 are sold at 40 70 frs. and choice, salmon coloured pieces 400500 frs. 

 and even more. 



In the Aquarium the Red Coral , inhabiting usually deeper waters 

 does not last long and is therefore generally not seen in a living condi- 

 tion. A specimen will be found enclosed in a small glass at the bottom 

 of tank 21. 



MEDUSA or JELLY-FISH. 



Those who come from northern seas and remember to have found 

 on the sands ugly and offensive masses of jelly , will find it difficult to 

 .associate these with the large Rhizostoma (Fig. 80) and Cotylorhiza 

 (Fig. 79), or with the smaller Pelagia (Fig. 81) . Tima (Fig. 82), O- 

 lindias (Fig. 84), Carmarina (Fig. 83) etc.; the living Medusae have a 

 very different appearance indeed. Their almost complete transparency, the 

 beauty of their movements, and often their brillant colouring, make them 

 very attractive objects. As they swim, they take the form of a mushroom 

 or an open umbrella , the regular opening and closing of the umbrella 

 driving them along. Round its edge are situated the sense-organs, pro- 

 bably of seeing and hearing. 



From the centre of the under surface of the umbrella hangs a long, 

 generally hollow, gelatinous stalk, also transparent; it is provided at the 

 end with an aperture, the mouth In some jelly-fish, however, the stalk 

 is short and divided into a number of small lappets, each of which bears 

 a mouth leading into a common cavity, the stomach. From the edge of 

 the umbrella hang down long tentacles, which the animal can at wil, 

 contract and elongate to a considerable extent. These tentacles are pro- 

 vided with numerous stinging-cells , such as have been described in the 

 case of the Actiniae ise p. 56); and, as there, they afford an efficient 

 means of defence for the delicate body. The unpleasant stings experien- 

 ced occasionally in sea-bathing are generally due to contact with these 

 jelly-fish. Some species, indeed , which attain a size of one to two feet 

 and a weight of 50 to. 60 pounds, can sting very seriously. 



A few species shine at night with a greenish light ; thus Pelagia 

 has received the specific name of noctiluca ( night-lantern ; not to be 

 confounded with the much humbler organism, which has Noctiluca for 

 its first name). Some species of fish spend the early part of their life 



