350 



Apltsiid.e.- 



-JIOLLUSCA.- 



-Ujibrellid.e. 



side lobes of the foot are dilated, and free for swiiiitniiig 

 (see Plate 4, fig. 1 — Aj>hjski punctata) ; and the shell 

 is subcartilagiuoiis and covered by the mantle. It 

 is oblong, convex, flexible, and translucent, with the 

 .opes acute and slightly iucurved. The species of 

 Sea-hares, or Aplysise, are rather numerous, upwards 

 of fort}' liaving been described; they are found inhabit- 

 ing the seas of the West Indies, the Mauritius, China, 

 the Mediterranean, Norway, and Great Britain. They 

 are chiefly vegetable feeders, living principally on sea- 

 weed. They are said to devour animal substances also ; 

 but Cuvicr, Pessonel, and others have sufficiently proved 

 that marine plants are their ordinary food. Dr. John- 

 ston tells us that be kept a specimen of the Aplysia 

 mustellna for nearly three months in a state of confine- 

 ment, during which it was fed on sea-weed alone, and 

 that it ate these greedilj', showing a certain degree of 

 jireferenoe for the dulse [Fucus palmatus). The 

 Aplysia is of quick growth, the MedileiTanean species 

 being said to attain its full size of about four inches in 

 one or two months. When irritated these animals pour 

 out an abundance of a fine pur])le-coloured fluid, so 

 much so that a single individual can colour the water 

 fur some yards around it. " This fluid is secreted in a 

 gland of a triangular figure, situated under the base of the 

 ilfshy coverlid of the branchia?, and oozes out from all 

 the free surface of this coverlid." — {Johnston.) Cuvier 

 says that, in drying, the secretion assumes the beautiful 

 deep hue of the sweet Scabious (Scahiosa alro-jmrpu- 

 rea), and remains nualtered by long exposure to the 

 air. The smell is faint; there is nothing peculiar to the 

 taste, nor has it any irritating quality, for it may be 

 a| plied a long time to the skin with perfect impunity, 

 liesides this innocuous purple fluid, the Aplysia; occa- 

 sionally discharge, though only in small quantities, a 

 whitish liquid of an acrid nature, which is secreted by 

 a gland composed of little round hyaline grains, and 

 emitted through a circular aperture opening externally 

 a little behind the aperture of the oviduct. On this 

 account, and from their grotesque forms, in olden times 

 they were viewed with fear and supei'stitious dread; 

 they were considered, by the Romans especially, as 

 possessing a deadly poison. " It was held, or was sup- 

 posed to hold," says Dr. Johnston, " such a noxious 

 sympathy with man, that the 'only aspect thereof was 

 poisonous to some ; to women great with child the sight 

 produced untimely labour, and hence it was employed 

 to discover concealed pregnancy ; the touch of it was 

 fatal, some sa}', to the man who handled, others to the 

 mollusc, which latter doubtless would be the more pro- 

 bable result ; while others affirmed only that the hair 

 fell from the parts with which it came in contact ; and 

 all agreed that the odious foetor which issued from the 

 body occasioned sickness and overturniugs of the sto- 

 mach. That such a creature should nfibrd a potent 

 poison was a reasonable inference ; and it certainly 



formed one ingredient of some of the poisonous draughts 

 so much resorted to in the corrupt daj-s of Rome. 

 Locusta used it to destroy such as were inimical to Nero; 

 it entered into the fatal potion which she prepared for 

 the tyrant himself, and which he had not resolution to 

 swallow ; and Domitian was accused of having given it 

 to his brother Titus. The ojjeration of the poison was 

 not iumiediate ; but the victim lived as many days as 

 the hare had lived subsequent to its removal from the 

 sea. What proportion of truth there is in this account 

 it is not easy to decide. I am not prepared to reject the 

 whole, as some modern authors have done, who believe 

 that the singular conformation of the Aplysia, and the 

 power it possesses of discharging at pleasure large 

 quantities of a fluid of the richest purple colour, have 

 given rise to the whole tale." Our British species ap- 

 pear to be perfectly inofiensive and quite harmless; but 

 there may be other species in warmer climates, which, 

 at i)articular times, may possess a fluid of deleterious 

 quality. Bubadtch, an author of some repute, mentions 

 that one species which abounds in the Bay of Naples, 

 (the Aplysia lep>wina), when removed from the sea 

 and placed in a vessel, exuded a large quantity of fluid 

 which exhaled a sweetish, sickening, peculiar smell. 

 When placed on a plate for the purpose of more nar- 

 rowly examining its structure, the room, he says, was 

 filled with a most fetid, nauseous odour, which he could 

 scarce endure without going out repeatedly to breathe 

 a purer air. His hands and cheeks swelled after hand- 

 ling the creature for any length of time, and when he 

 applied some of the liquid to the chin, the hairs fell from 

 the part touched. In a large species which occurs at 

 St. lago, in the Cape de Verd Islands, Mr. Darwin 

 informs us that, besides emitting a purple flui<l which 

 stained the water for the space of a foot around, it dis- 

 charged an acrid secretion from all over its body, wdiich 

 caused a sharp, stinging sensation similar to that pro- 

 duced by the Physalia or Portuguese man-of-war. 

 Aplysia depilans is the most common of the species in 

 our seas, and obtains its specific name from its supposed 

 depilatory powers. 



Family— UMBRELLID^ {Umhrdla Slulh.) 



The Umbrellas have a regularly calcareous, exter- 

 nal shefl, but very disproportionate to the size of the 

 animal. The foot is very large, thick, tubercular on 

 its sides; it is flat beneath and deeply notched in front. 

 In this fissure is placed the mouth, which is furnished 

 with a retractile proboscis. The shell is limpet-like, 

 orbicular, flattened, with a slightly raised, conical, sub- 

 central apex. Externally it is marked by concentric 

 lines of growth, and internally it has a central coloured 

 and striated disk. — See Plate 5, figs. 1, 2 (Umbrella 

 wnhellata and animal). 



Oedee II.— NUDIBRANCHIATA (= Gymnobeanchiata.) 



The Nudibranch or Naked-gilled Molluscs, or " Sea 

 Slugs," as they are frequently called, are all natives of 

 the sea. They have no shell in their adult state, and 



carry their gills, which are of various forms, on some 

 part of the back, exposed to the direct influence of the 

 water in which they live. They possess an elongate 



