68 C. J. CON X DLL V. 



finally examining them in glycerine. When examined under 

 higher magnification, the guanophores are seen to be spindle- 

 shaped bodies having an average length of about 20^ and a maxi- 

 mum breadth of 3 to 4/A. There are other smaller guanophores 

 or iridocytes, ovoid in shape being about n//, in length and 3 to 4/1 

 in width. These iridocytes are especially found in patches apart 

 from any association with melanophores and give rise to the mot- 

 tled condition of the male. When associated with melanophores, 

 the guanophores seem to acquire a more brilliant iridescence than 

 when they occur separately. The more common colors reflected 

 in the specimens adapted to a light background are yellow, orange, 

 and green. If the scales are removed, and examined under the 

 microscope, these iridescent points are not to be seen in the melan- 

 ophores, which remain on the distal portion of the scales after 

 removal. They are located on the proximal portion of the scale 

 and the reflected rays pass through the distal portion of the over- 

 lapping scale. 



It is well known that many animals show a green coloration 

 though there is no green pigment present. This is true of Fundu- 

 lus. The green tint is due to the combination of the effects of 

 melanophores and xanthophores over a layer which reflects blue 

 or over iridocytes possessing that physical property which Pouchet 

 termed " le cerulescence." When paraffin sections are made 

 through the skin there is to be seen a compact layer of cells occupy- 

 ing the inner part of the dermis next to the muscles. The cells 

 are rectangular in shape with their long axis parallel to the surface. 

 The nuclei are likewise elongate. Cunningham and McMunn 

 (1893) have suggested an ontogenetic relation existing between 

 this layer which they term the argenteum, and the iridocytes. 



There is also a close relation in structure and optical properties 

 between the guanophores of the integument and those of the peri- 

 toneum. The peritoneum of Punduhis is covered with dense 

 black pigment on the surface exposed when the body cavity is 

 opened, and the inner surface shows the typical silvery sheen. 

 This layer is more highly specialized than the reflecting layer of 

 the integument. It does not stain with anilin dyes. If the pig- 

 mented surface be examined by deflected light, the same phenom- 

 enon of brilliant points associated with melanophores is seen. 



