26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. ']2 



V. Arms with a median dorsal stripe. 



a. A broad median stripe, lighter or darker than the color 



on either side of it. 

 h. A narrow median stripe, always very dark. 

 VI. Arms conspicuously and regularly cross-banded. 



a. With several more or less irregular broad bands. 

 h. With a broad approximately central band. 



c. With broad alternating bands of equal width. 



d. With narrow alternating bands of equal width, 



e. With narrow well-spaced bands. 



As a general rule the coloration of the pinnules follows that of 

 arms, but in a few types they are banded on each segment and in at 

 least one case this is a good specific character. 



The cirri are usually unicolor, less commonly dull at the base, 

 becoming gradually or abruptly brighter distally, and rarely show 

 distinctive color types ; when this occurs the color types are usually 

 a reflection of the color types of the division series and arm bases and 

 very rarely distinctive. 



Particolored cirri, except those which are merely brighter distally, 

 fall into the following classes : 



I. Each cirrus segment with a transverse band. 

 II. Cirri unicolor, but of a color not found in the calyx or arms. 



III. Cirri blotched or spotted. 



a. Cirri with irregular blotches or irregular bands. 

 h. Cirri with small spots. 



IV. Cirri longitudinally striped. 



A study of the development of the colors seems to indicate that all 

 colors except gray and black may arise directly from white, and that 

 yellow, red and brown usually arise directly from white, while violet 

 arises as often from white as from any other color. All colors may 

 develop from yellow ; gray and black are developed only from yellow, 

 and purple and green arise more frequently from yellow than from 

 any other color. Red frequently develops into purple, and occasion- 

 ally into yellow, violet and green. Brown develops into green and, 

 less frequently, into violet. Orange develops into brown. 



At a depth of 55 fathoms in the sea the relative proportion of the 

 red rays is considerably diminished, and at 300 fathoms they have 

 almost completely disappeared. In a discussion of colors, color com- 

 binations and color types and their relation to depth, therefore, it 

 would seem that bathymetric divisions of 0-55 fathoms, 55-300 

 fathoms, 300-600 fathoms and 600 fathoms and over would be as 

 satisfactory as any. 



