4 JOURNAL OF MARINE ZOOLOGY AND MICROSCOPY. 



stellate form of much greater size that in the resting condition. 

 When exciting cause is gone, the muscles relax and the pigment 

 sac springs back to its normal spherical contracted state. What 

 Klemensievicz found was that the innervation or nerve supply of 

 these muscular fibres had its centres in the two peduncles or stalks 

 of the optic ganglia, that issue, one on either side, from the coalesced 

 ganglia functioning as the animal's brain. Moreover he discovered 

 that irritation of one of these centres caused immediate change of 

 colour in the corresponding side of the body. This implies a very 

 close connection between the sense of sight and the chromatophores 

 of the skin. Frequently have I seen an Octopus crawling among 

 brown Fucus of a tint absolutely similar ; anon as he darted away 

 from this hiding place among the weed, he paled and grew grey 

 as the sand over which the course lay. From what we know, the 

 alteration of colour would here be a reflex result working through 

 a visual perception of the alteration in the surroundings, passed 

 inwards to the centre having control of the pigment sacs.* I believe ' 

 the action to be purely involuntary, the adaptation being a process 

 too complicated and delicately precise to be coordinated consciously. 



In the same way the deep uniform chestnut-brown assumed 

 by the animal under the excitement of combat — which I have 

 frequently seen — is a reflex effect of the general nervous excitement 

 aroused in the whole system ; muscular contraction and not relaxation 

 being well known to be one of the chief constant characteristics of 

 strong emotion of this kind. 



Again in swimming, more than usual effort is put forth by the 

 Octopus — and this action characterised thus by vigorous muscular 

 contraction is performed by the animal always in a colour guise of 

 rich deep brown. When resting — which takes place usually during 

 daylight — the colour is generally pale. Illness too is accompanied 

 by great lack of colour. 



In connection with the phenomenon of parti-colouration, it is 

 interesting to note the following somewhat related instances. In 

 Guernsey Museum is a lobster coloured of a pale pink down one side, 

 but of the ordinary deep blue black upon the other. No special 

 dissection was made, but there is obvious reason to believe the cause 



* Since writing the above, it occurs to me that an alternative explanation can be given 

 by supposing that the chromatophores act as eye-spots ; that they themselves receive the 

 impression of change in the colour surroundings, pass it back by their nerves to the con- 

 trolling centres, which, upon this irritation, give out impulses bringing about alteration in 

 the form of the chromatophores, and consequent change in the body hue. But I doubt 

 this, principally because one would rather expect local colour change, than suffusion over 

 the whole body as does normally happen. We would expect the alteration to occur only 

 on that aspect turned towards the coloured objects of the environment, and this is not 

 what does happen. To settle this point, I purpose carrying out some direct experiments, 

 the results of which will be duly recorded, 



