NOTES ON ANIMAL COLOURATION, 



(Series I.) 

 BY JAMES HOENELL. 



I. On Lateral Independence in the Nervous Control of 

 Colouration in the Octopus. 



SELDOM have I been more surprised than when I first saw 

 parti-colouration in the Octopus. I had been watching one of 

 these creatures creeping slowly from point to point over the rock- 

 work of the large tank which it inhabited in company with four 

 others of its kin. In colour it was of the same dappled brown 

 characteristic of the others. But suddenly, without apparent cause, 

 the colour of the right side of the body as, too, that of the four 

 arms appertaining to that side, paled almost to snowy whiteness. 

 The division into coloured and uncoloured halves was absolute : had 

 the median line been drawn with mathematical accuracy down the 

 dorsal aspect, the division could not have been truer. This curious 

 appearance lasted close upon five minutes, and though I took every 

 opportunity of watching for its recurrence, nearly a week passed 

 before I was successful. In this second instance it was not the same 

 individual and the side that became deprived of colour was the left. 

 The distinctness of the bipartite colouring was fully as well marked. 

 Since then I have found by close observation that while by no 

 means frequent, still this colour control was possessed by all the five 

 specimens under observation. 



Complete functional independence so clearly marked as this, is 

 extremely unusual and it does not appear to have been noticed as 

 voluntarily practised by the animal in question. It has however 

 been observed as induced by artificial means during investigation 

 by Klemensievicz* on the nerve centres controlling the pigment 

 bodies or chromatophores of the Cephalopoda. These bodies — sacs 

 full of pigment — are each provided with a radiating set of muscular 

 fibres, which being excited, contract pulling the pigment sac into a 



* " Bcitrlige Zur Kenntniss des Farbcnwechscls der Cephalopoden," Sitzungsber 

 der Acacl. Wien, 1873. 



