108 CAROTINOIDS AND RELATED PIGMENTS 



fucoxanthin is present in these algae. The view of Kohl (1906) that 

 the leucocyan reaction is specific for carotin is hardly to be regarded 

 as tenable. The imperfect studies which have been made do not 

 indicate whether true xanthophylls are also included among the caro- 

 tinoids of the Bacili<iricci, but it is not unlikely that this will be 

 found to be the case when the matter comes to be examined in detail. 



The Peridinieae. The Peridiniales, also called the Dinoflagellata 

 comprise a relatively small class of unicellular algae, which are found 

 mostly in salt (sea) water. They sometimes form an important part 

 of the plankton of the sea, so that their pigments are of interest, as 

 in the case of the diatoms, on account of the part which the plankton 

 of the sea plays in the food of fishes and other marine animals. 



Schiitt (1890) appears to have made the only specific examination 

 of the pigments of the Peridinieae, but since his work was performed 

 before the most important developments took place in the field of 

 carotinoids it is necessary to interpret his observations in the light 

 of present-day knowledge of the subject. Up to his time the color 

 of the Dinoflagellates was regarded as due to the same pigment which 

 was believed to color the diatoms, namely, diatomin. As is now 

 known, diatomin is not a specific pigment. Although Schiitt did not 

 recognized this fact he did point out that the color of the Peridinieae 

 is more reddish-brown and easily distinguished from the yellowish- 

 brown color of the diatoms. This difference in tint was found to be 

 due to the presence of carmine colored drops or globules in many of 

 the Peridiniece examined, in addition to the yellowish-brown pig- 

 ment in the chromatophors of the algae. 



The Peridiniece examined by Schiitt were Gymnodinium Helix, 

 Dinophysis acuta, D. laeris, Certium tripos, C. fusus, C. furco, Peri- 

 dinium diver gem, Prorocentum micans, and Glenodinium species. In 

 addition to brownish-red and brownish-yellow water extracts, the 

 pigments of which were regarded as analogous to the phycoerythrin 

 of the Rhodophyceae and the phycophain of the Phaeophyceae, re- 

 spectively, a wine-red alcohol extract was obtained. The pigment 

 thus extracted, which could not have been pure, was soluble in ben- 

 zene, ether, chloroform, carbon disulfide, and glacial acetic acid, but 

 very little soluble in petroleum ether. Schiitt regarded the pigment 

 as analogous to diatomin, and called it peridinin. The slight solu- 

 bility of the pigment in petroleum ether and ready solubility in alco- 

 hol suggests that a xanthophyll-like pigment predominates in the 

 Peridinieae. It is not possible, to draw more specific conclusions than 



