THE CHROMATOPHORES OF ANIMALS. 119 



in support of the generally accepted view. It is difficult, 

 in the short space at my disposal, to do justice to this 

 author's valuable memoir, but the following observations 

 made by him may be quoted. The radial fibres are thin 

 and band-like during the contracted condition of the chro- 

 matophore, but broader during the expanded condition. In 

 embryonic chromatophores the number of radial fibres is 

 less than in fully developed chromatophores ; and, in 

 correlation with this, the chromatophore in expansion 

 exhibits fewer processes or angles in the embryonic con- 

 dition than when fully developed. Each process of the 

 pigmented cell corresponds to a radial fibre, and has every 

 appearance of having been caused by the pulling out of the 

 membrane of the central cell by the radial fibre at that 

 point. This fact, together with that of the shortening and 

 widening of the radial fibres during the expansion of the 

 chromatophore, renders inevitable the conclusion that the 

 expansion of the chromatophore is determined by the con- 

 traction of the radial fibres. Moreover, in spite of Harting's 

 statement to the contrary, there can be no doubt about the 

 fact that the process of expansion of the chromatophore is 

 much more rapid than the process of contraction. 



I may add that from observations made at Plymouth 

 during the present summer, I have been able to satisfy my- 

 self of the correctness of all these observations, and at the 

 same time to make others which have convinced me that 

 the radial fibres are the active agents in the expansion of 

 the chromatophore. If a piece of the mantle of a young 

 Loligo media be placed in a weak solution of methylene 

 blue, the tissues are gradually impregnated with the dye, 

 and the radial fibres are eventually paralysed in the con- 

 tracted condition. But it frequently happens that the 

 fibres of one side of a chromatophore take up the pigment 

 and are paralysed before those of the opposite side, in which 

 case it is possible to observe a curious phenomenon. One 

 half of the chromatophore remains permanently expanded 

 to its full extent, while the other half displays the usual 

 phases of alternate expansion and contraction. II it be 

 true, as Harting, Blanchard and their supporters maintain, 



