702 RECORD OF CURRENT RESEARCHES RELATING TO 



wliich are scattered throtigli tlie integument. It is to Kollikcr, liow- 

 ever, that we owe our first instalment of definite knowledge as to the 

 structure of these bodies, inasmuch as it was he who directed attention 

 to the presence of the radial contractile fibres, by the contraction of 

 which the pigment spots are extended. A number of other observers 

 have held similar views, and of these we need only refer to Briicke who 

 pointed out the curious diiference which obtains in the Cei^halopod as 

 compared with the chameleon ; in the former the active state of the 

 pigment spots finds its optical expression in their darker, while in the 

 reptile it is in the brighter coloration. Other observers, such as 

 Harting and Waldeyer, regard the play of colour as due to the proto- 

 jDlasmic substance of the chromatophore, and to that only. The 

 question is now treated by Dr. Klemensiewicz, whose essay may be 

 divided into two portions : — 



Structure of the Chromato'pliore. — In this body we may make out 

 the following parts : (1) A central pigment spot ; (2) Its cellular 

 envelope ; (3) Radial fibres, set in a plane parallel to the surface of 

 the integument and attached by their broadened conical ends to the 

 pigment body ; (4) The cavity of the chromatophore, which is separated 

 from the dermal tissue by a thick layer of connective tissue. The 

 examination of fresh specimens and of embryonic stages, together with 

 specimens prepared by the aid of alcohol and gold chloride, has led 

 the author to agree ^-ith Kolliker in regarding the pigment body as 

 being a naked cell, for on no occasion has he been able to observe the 

 structureless membrane described by Boll. As already stated, there 

 is, however, a covering to the cell, which is partly formed by the 

 cellular envelope described by Boll, and partly by the insertions of 

 the radial fibres; in the contracted state this investment forms a 

 hollow sphere with outwardly projecting processes ; it consists of 

 several layers of cells, between the elements of which there pass the 

 insertions of the radial fibres. No very definite results were attained 

 to with regard to the disposition of the nerve-fibres, as the author was 

 not able to make out any direct connection between them and the 

 pigment body or the radial fibres ; the question is however one of very 

 great diificulty from a histological point of view, but we shall see 

 directly how great is the connection which can be made out by the 

 physiological method of investigation. As to the coloration of the 

 chromatojjhore it is now known that this does not only difi'er in difterent 

 species, but even at difi"erent stages in development ; thus in Loligo 

 vulgaris it is reddish in the embryo, but violet in the adult. Of 

 course, also, it differs in different stages of contraction, and thus while 

 it is violet when expanded, it is dark brown or black when con- 

 tracted ; the form too is different, for the thin plate seen in the ex- 

 panded stage is brought into a more or less rounded form in the con- 

 tracted condition of the chromatophore. The radial fibres similarly 

 differ in form, being thin and lamellar when the chromato2:»hore is 

 contracted, but broader when it is expanded ; they are enclosed in a 

 fine structureless membrane. The cavity (4) is chiefly filled with 

 fluid. The histological differentiation of the body may be shortly 

 summed up in saying that the pigment-spot is formed of a single cell, 



