M L L U S C A. 



from a complex glandular body, and unites with the 

 common canal. This common duct, before it reaches 

 the external orifice, receives the contents of the pedun- 

 culated vesicle, and has attached to it a hotryoidal 

 glandular organ, whose use is unknown, but which 

 aoroe suppose to be employed to secrete an acrid liquor 

 regarded as venomous. 



It is obvious from this structure, that the seminal 

 fluid and eggs must come in contact in the common 

 canal, and at the single orifice, provided they are both 

 ejected at the same time. From the orifice to the right 

 fore-feeler there is a sulcus, leading to the pore con- 

 taining the retractile penis. This organ, like those o 

 the other uiollusca, is solid. It terminates in a small 

 filament. The external groove is the only connection 

 between it and the other sexual organs. 



There is a peculiar secretion of a purple fluid, which 

 here deserves to be recorded. It issues from a spongy 

 texture, underneath the free side of the dorsal plate. 

 Connected with thU cellular reservoir is a glandular 

 body of a considerable size, which is supposed to se- 

 crete the coloured fluid. This gland is supplied by 

 a large branch of the glandular aorta, and gives out 

 two very large veins to the left vena car*. 



The purple fluid itself has never been carefully in- 

 sre**Jg*ted. It is not altered by the air after drying, 

 nor is its colour destroyed by acids or alkalies, although 

 the tint is a little changed, and rendered less pure. 

 Both these re-agents precipitate from the fluid white 

 flakes. 



This liquor M poured out by the animal when in 

 danger or constrained, and colours the water for seve- 

 ral yards around. It ejects it readily when put in 

 freaa water ; and when entangled in net, several 

 yards of it in the neighbourhood are sometimes 

 stained, greatly to the amazement of the unsuspecting 

 fishermen. 



The Aplysia has been long known in the records of 

 superstition under the name of the Sen Hare. Its 

 fleifa, and the inky fluid it pour* out, have been re- 

 garded M deleterious to the human frame. Even to 

 i it was supposed to occasion the loss of the hair ; 

 while the sightot it would not fail tosubduethe obstinacy 

 of concealed pregnancy. The progreM of science has 

 exposed the errors, or perhaps tricks of the earlier ob- 

 server*, ami proves the innocence of an animal former- 

 ly invested with every repulsive and noxious attribute. 



The specie* of this genus are still involved in great 

 obscurity. Those which inhabit the British isles ap- 

 pear to be the following. 



1. Apiyna depilant. Dorsal plates covered in the 

 middle. Body of a purplish- brown colour, with black 

 doU. Length from five to six inches. 



This i* the most common species, and is found from 

 the south of England to the shores of Zetland. It has 

 a faint disagreeable smell. 



2. Apfyna punctala. Body brown, with numerous 

 white spots. Dorsal plate exposed in the middle. 

 About the same size as the preceding. 



This species was first figured and described by Cu- 

 vier. who regards it as distinct. The characters by 

 which they are separated, however, are far from being 

 trustworthy. 



The colour in the depilan* is subject to considerable 

 variation, and in some eases the black spots disappear. 

 The absence of the cuticle from the middle of the dor. 

 al plate in the punctata, is probably the effect of ac. 

 cklent or age. 



Both kind* were observed by the late George Mon- 



tagu, Esq. on the Devonshire coast, and from a letter Mollusc.?. 

 of his now before us, dated 17th February IS 11, he > "^V^ 

 appears to have convinced himself that they did not 

 constitute distinct species. The question caa only be 

 decided by the discovery of the intermediate varieties. 



3. Aplysia viredit. This species is figured by Mon- 

 tagu, Linn. Trans, vii. tab. vii. f. 1. and described 

 in the following terms : " With the fore-part of the 

 body like a common Umax : teutacula or feelers two, 

 flat, but usually rolled up, and appear like cylindric 

 tubes ; at a little distance behind the tentacula, on each 

 side, is a whitish mark, in which is placed a small 

 black eye : the body is depressed, and spreads on each 

 side into a membranaceous fin, but which graduallyjde- 

 creases from thence to the tail, or posterior end : this 

 membranous part is considerably amorphous, but is 

 usually turned upwards on the back, and sometimes 

 meeting, though most times the margins are reflected ; 

 this, as well as the back, is of a beautiful grass-green 

 colour, marked on the superior part of the fins or 

 membrane with a few small azure spots, disposed in 

 rows ; the under part with more numerous, but irre- 

 gular spots of the same : the fore-part of the head is 

 bifid; the lips marked by a black margin: the sn.-ten- 

 taculum is scarce definable, as it most commonly holds 

 by a small space close to the anterior end, and turns 

 the posterior end more or less to one side : it some- 

 times, however, extends itself for the purpose of loco- 

 motion, in which it scarce equals a snail." 



" Although this animal does not strictly correspond 

 with the characters prefixed by Linnteus to the - 

 Laplytia, yet it approximates so nearly to the Depilr.ns 

 in its external form, that we cannot hesitate to place it 

 with that animal, though we could not discern any 

 membranaceous plate or shield under the skin on the 

 back." 



The characters here assigned to this species are such 

 as to excite the belief that it is not an Aplysia ; but 

 they are not sufficiently minute to enable us to esta- 

 blish another genus for its reception. It is to be hoped 

 that some naturalist who has an opportunity of visit- 

 ing the south coast of Devon, where this species was 

 found, will re-examine it* characters, and communicate 

 a more detailed account of its form and structure. 



III. DOLADELLA. This genus differs from Aplysia, Dni.-.' 

 in the dorsal plate being calcareous and hard. The 

 fore-part of the hotly is narrow behind, it is larger, 



and truncated obliquely. The disk thus formed is 

 circular, surrounded with a fringe of fleshy filaments. 

 From the centre of tliis disk, a longitudinal slit extends 

 forwards a little way beyond the anterior margin, and 

 contains the branchite. The position and structure of 

 the other organs are precisely similar to those of the 

 Aplysia. 



This genus was instituted by Lamarck, from cha- 

 racters derived exclusively from the dors.il plate or 

 shell. Cuvier afterwards examined a species brought 

 from the Mauritius by Peron, which he considers as 

 the species figured by Rumphius in his Arnboinshe 

 Rariteitkamer, tab. x. No. 6. and which he has con- 

 secrated to his memory, naming it Dolabella Runiphii. 



IV. NOTARCHUS. Thw gnus is destitute of the Notarchui. 

 dorsal plate, and contains an oblique groove on the 



neck, leading to the branchiae. The internal structure 

 resembles the Aplysia. This genus was instituted by 

 Cuvier, in his Regne Animal, Vol. ii. p. 395, and the 

 only known species described, IV. Tab. xi. f. 1. 



V. BULLA. The animals of this genus differ from Bulls, 

 the preceding, in the absence of wnUcula, and in the 



