Scientific Notices. 141 



the differences arise merely from accidental and varying causes. M. 

 Lesson's logick, which seems to be of the same school as that employed 

 in the before mentioned affair of the noses, will not be admitted as con- 

 clusive in such cases. Fact, and fact only, not random assertions, must 

 decide the case. This mode of dictation, founded on such logick, has 

 not yet become the statute law of Zoology. When it is established as such, 

 Mr. Vigors and Dr. Horsfield will make any admission that is asked of 

 them. — They will admit their Scinrus Raffiesii to be M. Desmarest's 

 Sciurua Prevostii; black to be white; or M. Lesson to be a Linnajus. 

 Until however that happy epoch dawns upon Natural History, they beg 

 leave to entertain their doubts upon such points. 



Mutations of Colour in Sepia and Coryphcma. 



One of the flattened kind of Sepia, brought me by an Indian at Ouhii, 

 interested my attention by the nut-brown spots Aviih which the gelatinous 

 surface was sprinkled, as they continued for some hours after the death 

 of the animal to disappear and re-appear alternately, like a pigment 

 when first thrown upon a mucilaginous medium ; as for example, in 

 marbling paper upon a decoction of aniseed. This made me think that 

 the colouring matter floats in a mucous fluid, corresponding in position 

 to the rete mucosum of other animals; and by its atomic attraction col- 

 lected itself into circular spots. 



Wherever the skin was touched a number of minute specks immedi- 

 ately followed the impression, occasioned, as I conjectured, by the mu- 

 cous matter which before concealed the pigments being pressed away, 

 and thus leaving it free to obey the laws just alluded to. 



This remark will help us to understand something of the process by 

 which those admired mutations of colour in the dying Corypheena are 

 brought to pass : supposing the death of the animal to alter the condition 

 of the mucus, the contained pigment vrill, of course, alter its arrange- 

 ment, and admitting the undulatory nature of the propagation of light, 

 all the various alterations of colour may be accounted for by having re- 

 course to the theory of Huygens, as expounded and illustrated by Dr. 

 Young and Mr. Herschel. J. T. L. 



