120 SCIENCE PROGRESS. 



that the expansion of the central pigmented cell is due to 

 some inherent amoeboid power residing in the cell itself, 

 such a phenomenon as this would be in the highest degree 

 remarkable. For it would imply that one half of the cell 

 was dead, or had at any rate lost its normal contractility, 

 while the other half was perfectly healthy. It is more fully 

 consistent with the phenomena to hold that the one half of 

 the chromatophore remains expanded because the radial 

 fibres which are attached to it are contracted and dead, as 

 their deep impregnation with the methylene blue enables 

 one to see, while the other half of the chromatophore is still 

 capable of the ordinary changes of form because the un- 

 stained fibres attached to it are still alive and capable of 

 relaxation as well as of contraction. I have even seen 

 instances of chromatophores in which the entire protoplasm 

 of the pigmented cell was dead, and in which the pigment 

 granules were aggregated into irregular patches and streaks 

 instead of being evenly distributed. In such cases it some- 

 times happened that one or two of the radial fibres, which 

 had taken up relatively little of the stain, could be seen to 

 contract from time to time, entailing a corresponding ex- 

 tension of the central cell in the region of their attachment. 

 The agency of the radial fibres in the expansion of the 

 chromatophore may accordingly be regarded as satisfactorily 

 established. 



The exact innervation of the chromatophore has not 

 yet been conclusively demonstrated. Harting's suggestion 

 than the radial fibres are nervous in nature has been seen 

 to be groundless by every subsequent observer ; but 

 Kliemensiewicz, in spite of many preparations, was unable 

 to find any nerve-fibrils supplying either the central pig- 

 ment-cell or the radial muscle-cells. That some kind of 

 innervation exists, however, is perfectly certain from the 

 physiological experiments of Leon Fredericq (iS), Klie- 

 mensiewicz, and Krukenberg (19). Fredericq showed that 

 the motor centre for the chromatophores resides in the sub- 

 oesophageal nerve-mass, a conclusion confirmed with an 

 abundance of new detail by Kliemensiewicz in the following 

 year. From the chromatophoric centre pass motor fibres 



