102 SEA-SIDE STUDIES. 



animal manifest precisely the same contractions and 

 expansions wliicli they manifest on the living animal, 

 it is clear that their activity does not depend upon the 

 " will," — a conclusion which elementary principles of 

 Biology ought to have made self-evident a priori.^ 



But it is not in Zoology only that logic is courage- 

 ously assaulted by man's " large discourse of reason." 

 If ''reasoning correctly on false premises" be the true 

 definition of madness, we are all more or less mad- 

 men ; although we are all " astonished '' at the insanity 

 which we do not share. Last evening this was brought 

 before me in half-sad, half-ludicrous aspect. We were 

 smoking, in the indolent beatitude of digestion, when 



* Delle Chiaje, in his Descrizione e notomia degli animali inverte- 

 hrati della Sicilia Citeriore, i. p. 15, says that the expansion of these 

 colour-specs is due to an expansile liquid, allied to blood — espansile 

 umore {ematosina 1) which is contained in the vesicles, and which is pro- 

 bably in relation with the blood-vessels and the rete Mal'pighi ; and he 

 suggests that its contractions and expansions may depend on respira- 

 tion. But the fact, recorded in the text, of a strip of skin taken from 

 the dead animal exhibiting the same contractions and expansions as 

 those exhibited by the skin of the living animal, shows that the con- 

 tractility of these vesicles is independent of any such cause, Kolliker 

 has shown that the contractions are produced by pale muscular fibres. 

 Some doubt, however, is permissible respecting their muscular nature. 

 As Charles Robin says, they are perfectly homogeneous and extremely 

 fine ; moreover, they are not capable of being isolated as fibres, " en 

 sorte qu'il serait plus juste de dire que les chromatophores (co}o\ired 

 specs) sent entoures d'une substance homogene contractile, fibroide ; 

 les fibres non isolables, et dont par suite le diamfetre exact ne peut etre 

 donne, sent disposees par faisceaux." f No one has explained how 

 these retain their contractility so long after all the other muscles. 



t Note communicated by Lebert in his •'Memoire sur la Formation des 

 Muscles." — Annales des Sciences, 1850, p. 172. 



