MEDUSAE OR JELLY-FISH. 37 



animal substances of larger dimensions, arc imbibed, and form 

 the nutriment of the animal. In the genus Cyanea, which is 

 so extremely abundant on our coast, the food is taken by one 

 four-lipped mouth, and is of a coarser kind, consisting prin- 

 cipally of Crustacea and small fishes. A provision for throwing 

 off the undigested portions is therefore required, and we ac- 

 cordingly find that no less than eight canals lead from the 

 centre of the disc to the outer margin, and are appropriated 

 exclusively to this use; an apparatus which, in the other 

 genus, was not wanted, and which, accordingly, had no 

 existence. 



To the minute and laborious researches of modern natu- 

 ralists, we are indebted for a knowledge of the fact, that the 

 sexes in these animals are separate, and that the ova, or eggs, 

 undergo a singular and highly interesting series of trans- 

 formations before assuming the likeness of the parent. 



The species of Medusa most abundant on our coasts during 

 the early part of the summer (Cyanea auritci) is well known 

 by the four conspicuous lunar or heart-shaped figures which 

 it exhibits. These are of a pinkish or purplish colour, and 

 are, in fact, the ovaries. Four pouches arc observed on the 

 lower surface of the body. To these the young, at a certain 

 period, are transferred from the ovaries, and undergo a 

 species of development analogous to that of the young qua- 

 drupeds of Australia in the marsupial pouch of the mother. 

 After changes in their size and colour, they exhibit a change 

 of form, become clothed with vibratile cilia, and, leaving the 

 maternal pouch, swim freely about, the larger extremity being 

 always in advance (Fig. 21). The little creature soon at- 



21. 22. 23. 24. 



DEVELOPMENT OF THE MEDUSAE. 



tnches itself to some fixed object (Fig. 22), and four arms 

 appear, surrounding a central mouth (Fig. 23). The arms 

 lengthen, four additional ones arc developed, all arc highly con- 

 tractile, covered with cilia, and actively employed in the capture 



