HARDWICKE'S SCIENCE-GOSSIP. 



219 



each side about six hepatic papillce, which are large, 

 spindle-shaped, and studded with four or five whorls 

 of pointed worts, each tipped by a crimson spot ; the 

 dorsal tentacles are thin, transparent, cut short at the 

 top, and rise out of long trumpet-shaped sheaths ; the 

 colours are yellow and crimson ; the tongue is slender, 

 and bears over a hundred recurved, denticulated 

 teeth arranged in single series ; this species flits oc- 

 casionally ashore, but it resides more frequently among 

 the branches of the beauteous corallines which em- 

 bellish the floor of the deep open sea. 



In addition to the Doridce and the Eolidre, there is 

 a third family, the Tritonidce, which embraces a few 

 British and foreign forms not less lovely, though 

 rather more eccentric in shape, than those already 

 delineated. This family is distinguished by the 

 possession of fringed, feathery, or warty special gills 

 distributed along the sides of the back ; and it is im- 

 portant to observe, that although these specialised 

 gills surpass those of the Doridce in extent of surface 

 exposed to the aeration of the water, yet they do not 

 equal them in the perfection of their anatomical rela- 

 tions, for there exists a communication between the 

 different branchial veins and the open spaces of the 

 skin which contain venous blood ; and, moreover, the 

 body of the animal has no secondary processes to 

 increase its extent of surface, and sowise materially 

 assist in the process of respiration. The tentacles in 

 this group are retractile into sheaths ; the stomach 

 in all the species is quite simple, and the liver com- 

 pact ; and the tongue has a central tooth and several 

 lateral teeth. The members of this family inhabit 

 great depths, but among these we will merely mention 

 Tritonia Hombcrgi and T. plebeian the former of 

 which sometimes attains the length of six inches or 

 more ; also ScylLza pdagica, with its curious wing-like 

 lobes, its long, narrow, and channeled foot, adapted to 

 clasp sea-weed, its beautiful tongue rows of seventy- 

 one denticulated teeth, and its curious gizzard, armed 

 with horny, knife-like plates. 



The fourth and last family of British Nudibranchs 

 is Elysiadae, wherein there are no special gills and 

 no distinct mantle, the i^espiratory function being 

 effected by the dense shrubbery of vibratile cilia 

 which clothes the entire surface of the body ; the 

 hepatic organs are branched, extending the whole 

 length of the body, and open into the sides of the 

 stomach ; the eyes are seated on the sides of the 

 head, the tentacles are simple or obsolete, and the 

 mouth is armed with a single series of teeth which 

 are disposed in a circle, like those of a circular saw ; 

 tlie heart has an auricle behind, and there are traces 

 of arteries and veins. 



We have seen how comparatively trivial and insig- 

 nificant are the instincts or mental faculties displayed 

 by these sea-slugs. The instinct of seeking and 

 occupying of places suitable to the procuration of 

 food, or.. for defence against the.. enemy, low unde- 

 veloped powers of sight, touch, taste, smell, and 



possibly hearing ; some are carnivorous, fierce, and 

 voracious, others dilatory, sluggish and sociable, but 

 very little of importance can be gleaned relative to 

 this matter. But there is a question of profounder 

 and more general interest involved in the economy of 

 these creatures, a speculation that to-day agitates 

 the most ingenious of our philosophical zoologists. 

 When we contemplate the peerless beauty and 

 symmetry of form and the gorgeous colouring of 

 these lowly denizens of the ocean, we are naturally 

 induced to consider, why it is that they are neverthe- 

 less compelled to "hide their light under a bushel," 

 or (to vary the expression) to " waste their sweetness 

 on the desert air " ! How is it that such forms of 

 exquisite beauty and delicacy, of such " fair propor- 

 tion," some of the loveliest treasures that embellish 

 old Neptune's bejewelled palaces, are not to be found 

 save by diligent and skilful search ? that they bury 

 themselves in inaccessible nooks, among rocks, 

 gullies, and ledges of the seashore, or upon the silent 

 bed of the ocean " full fathom five," unseen by men, 

 by those who, of all God's creatures, are most competent 

 to perceive and enjoy such aesthetic excellencies ? Can 

 we trace or imagine any relation between the beauty of 

 these animals and any function which is essential to 

 their life or existence ? Or is their ornament and 

 variety of form and colour bestowed upon them by 

 the Creator merely for the sake of these qualities, and 

 without any reference to utility of any kind whatever ? 

 Are these ostentatious colours of any service in regard 

 to protection, concealment, or warning ? Are they 

 caused by the direct action of climate, soil, or food ? 

 Are they due to a prodigality of life-energy effecting 

 great and rapid development in certain tissues, &c. ? 

 And, finally, is sexual selection concerned in their 

 production in any way ? Mr. Darwin and his dis- 

 ciples would endeavour to resolve all beauty into 

 utility, i.e. all animal beauty is of some use in the 

 economy of the animal, or is indispensable to some 

 function to be effected during its life-history. That 

 eminent biologist has been led to the ridiculous con- 

 clusion, that active or voluntary sexual selection is 

 one of the chief causes, if not the chief cause, of all the 

 variety and beauty of colour we see among the higher 

 animals. Mr. Wallace thinks that the need of protec- 

 tion, &c., is a far more efficient cause of variation of 

 colours ; and he considers that colours are produced or 

 intensified by processes of development, as where, for 

 instance, there is a^surplus of vital energy, &c. This 

 latter view has the ring of soundness ; but perhaps 

 it is only a specialised or [modern physico-material 

 edition or modification of what loomed before the 

 minds of some of the old Greek philosophers, when 

 they proclaimed that beauty is merely the outward 

 expression of some form of good or perfection, or 

 that it is the outward manifestation of the true or the 

 good. The man or the animal that is in the truest, 

 best, aad most harmonious condition, i.e. in the most 

 healthy condition of body and mind, is certain to 



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