CONTRIBUTIONS FROM THE BERMUDA BIOLOGICAL STATION 



FOR RESEARCH, NO. 62. 



ON THE PIGMENTATION OF A POLYCLAI). 



W. .]. CROZIEH. 



Received Feb. 0, 1917. Presented by E. L. Mark. 



AMONG early naturalists it was quite commonly held that in many 

 cases the coloration of marine invertebrates, such as turbellaria, was 

 directly determined by that of the pigmented substratum upon which 

 they fed. In this way it was attempted to account for certain con- 

 spicuous resemblances between the color of species living in company 

 with sponges, ascidians, and the like, and that of the organisms over 

 which they crawled. Furthermore, these color agreements have 

 frequently been considered valuable to the species concerned, accord- 

 ing to the scheme advocated by the general theory of protective col- 

 oration (cf. Potts, 1915). Increasing knowledge of animal pigments 

 has, however, served to develop a well-founded distrust of so simple 

 an explanation for correspondencies in the pigmentation of associated 

 forms. Several instances have recently come to my notice which 

 seem of interest in connection with the idea of the origin of color in 

 certain invertebrates from the pigmentation of their food. In the 

 one notable case of color agreements which has been adequately studied 

 (the prawn Hippolyte), this view has been decisively rejected (Gamble 

 and Keeble, 1900; Gamble, 1910). 



The present observations concern a polyclad turbellarian, Pseudo- 

 ceros sp., found in association with various tunicates, upon the surface 

 of which it has been seen to feed. This flatworm, of which the general 

 characteristics may be gathered from the figures, apparently belongs 

 to the genus Pseudoceros; but it does not agree with the diagnoses 

 of any of the four species of this genus which Verrill (1900, 1901) has 

 described from Bermuda. 1 I must refrain from attaching a name to it 

 until its anatomy shall have been studied. 



This form seems not to be common at any time of year. Although 



1 Several of Yen-ill's species were founded, apparently, on color differences 

 of single specimens. 



