4 i4 THE GLAUCUS. 



The DENDRONOTUS derives its very appropriate name from two Greek words, the 

 former signifying a tree, and the latter the back. The beautiful branched gills are set 

 in a very shrub-like fashion upon the back, and even the tentacles and appendages of 

 the head are branched so as to correspond with the gills. In this and many other species 

 the digestive organs are covered with prolongations, which are carried into the little 

 tuberculated appendages which stud the surface, and have given cause to M. de Quatre- 

 fages to establish his theory of " phlebenterism," which he defines as " an anatomical 

 arrangement which is generally characterized by ramified prolongations of the digestive 

 tube, in virtue of which the digestive apparatus, to a certain extent, supplies the place 

 of the circulatory apparatus, and aids in the process of respiration." 



In his " Rambles of a Naturalist," Vol. I. note xv., the same author makes the 

 following valuable remarks : " At the same time I found in the Eolidinae a heart and a 

 tolerably well developed arterial system, but I could not distinguish any veins ; never- 

 theless, I was so imbued with the ideas of Cuvier, that it was long before I was willing 

 to admit the non-existence of these vessels. Nor was I convinced that there were 

 really no veins in the Eolidinae, until I had followed the same blood-corpuscule through- 

 out its entire circuit until I had seen it issue from the heart and pass through the 

 arteries by whose walls its movements were regulated, and until it was conveyed through 

 every part of the general cavity and finally carried back to the heart." The whole 

 subject is too complicated and detailed to be here investigated, but it is of too great 

 importance to have been left without a brief notice. 



THE central figure at the bottom of the illustration represents the beautiful DOTO, 

 here shown in the act of making prey of a sea-anemone, which in vain withdraws its 

 tentacles and contracts itself into a shapeless mass at the touch of an enemy. It may 

 be here remarked that the word Doto is the name of one of the sea nymphs of mythology, 

 and that in consequence of their exquisite coloring and beautiful forms, the names of 

 nearly all the nymphs have been given to different species of nudibranchs. The ten- 

 tacles of this animal are slender and can be retracted into certain trumpet-like sheaths, 

 which are seen projecting from the body. In this creature the processes of the diges- 

 tive system pass into the large appendages on the back ; and it is a curious fact that 

 although they fall off when the animal is handled, they are soon reproduced, and the 

 creature seems to suffer little inconvenience from their loss. Examples of this creature 

 can be found on the British coasts. 



THE remaining figures are representatives of another family, called the Eolidae. In 

 these creatures the theory of phlebenterism finds its best proofs, as the processes of 

 the digestive organs extend throughout the beautiful projections on the back, even 

 though, as in one genus, they are placed on footstalks. 



The beautiful EOLIS is common on our own coast, and may be seen moving over the 

 plants and stones with tolerable activity, and always keeping their tentacles and papillae 

 in motion, sometimes contracting and sometimes extending them, while the movement 

 of the water causes them to wave in a very graceful manner. These papillae possess the 

 property of discharging a milky kind of fluid when the animal is irritated. The fluid, 

 however, is quite harmless, at all events to the human skin. As in the previous case, 

 the papillae are liable to fall off at a touch. While using the dredge, the naturalist is 

 sure to bring plenty of nudibranchs to the surface ; but, owing to their habit of con- 

 tracting themselves into a shapeless mass, an uninitiated observer will probably fail to 

 notice them and fling them overboard again, together with the seaweeds, stones, and 

 other refuse substances. The Eolis is a voracious being in spite of its delicate beauty, 

 and if several of them are kept in a vessel and not supplied with the sertularia and 

 other zoophytes on which they feed, they will attack and devour each other. 



OUR last and most remarkable example of the nudibranchs is the GLAUCUS, or SEA 

 LIZARD, the strange creature in the upper left-hand corner. In this animal the gills 

 are slender, cylindrical, and supported on three pairs of lobes or footstalks. 



