NOTE -BOOK OF A NATURALIST. 347 



in all the vesicles, but, in general, corresponds more or 

 less closely with the tint of the secretion of the ink-bag 

 with which this race is furnished as a protection ; for, as 

 is known to all who have observed their habits, their first 

 act when surprised is to eject this inky fluid, succus 

 nigrce loliginis, that they may escape under cloud of the 

 discoloured water. In the common cuttle. Sepia, besides 

 the vesicles which correspond to the ink in the colour of 

 their contents, there is another series of an ochre colour. 

 In the common pen-and-ink fish, Loligo vulgaris, there 

 are three sorts of coloured vesicles, yellow, rose-red, and 

 brown. In Loligo sagittata, there are four kinds — saf- 

 fron, red, blackish, and bluish. The paper Nautilus, 

 Argonauta Argo, possesses vesicles of all the colours 

 which have been observed in other cephalopods, and 

 hence the variety and change of colour which its skin 

 presents when exposed to the light. The rest of this in- 

 teresting organization will be best conveyed in the Pro- 

 fessor's own words: — 



These vesicles have no visible communication either with the 

 vascular or the nervous systems, or with each other; yet they 

 exhibit during the lifetime of the animal, ami long after death, 

 rapid alternating contractions and expansions. If, when the 

 animal is in a state of repose, and the vesicles are contracted and 

 invisible, the skin be slightly touched, the coloured vesicles show 

 themselves, and in an instant, or sometimes with a more gradual 

 motion, the colour will be accumulated like a cloud or a blush 

 upon the irritated surface. If a portion of the skin be removed 

 from the body and immersed in sea-water, the lively contractions 

 of the vesicles continue; when viewed in this state under the 

 microscope by means of transmitted light, the edges of the vesicles 

 are seen well-defined, and to pass in their dilatations and con- 

 tractions over or imder one another. If the separated portion of 

 integument be placed in the dark, and examined after a lapse of 

 ten or fifteen minutes, all motion has ceased ; but the vesicles, 

 when re-exposed to a moderately strong light, soon, in obedience 

 to that stimulus, re-commence their motions. As the vibratile 

 microscopic cilia have been recently traced through the higher 

 classes of the animal kingdom, it is not an unreasonable conjecture 



