ANIMAL CHLOROPHYLL B41 



pigment granules which colour the nudiliranch C h r o m o d o r i s 

 zel)ra are also to be found in great abundance in the pigment 

 cells of the blood — the identity of the two pigments having 

 been determined by the spectroscope ; (3) lastly, while ex- 

 amining the body-fluid of one of the common sea-urchins, 

 Tripneustes esculent us, it was found that the large 

 red amoeboid cells (so well described by Geddes, 1S80) gave 

 strong indication that their pigment is the same as that which 

 colours their spines and tube-feet. Thus, in a tunicate, a 

 mollusc, and an echinoderm there seemed to be very good 

 evidence that the body-pigment is found also in the l^lood. 



The experimental work was carried on at the Bermuda 

 Biological Station for Research during the summer of 1020, 

 and I wish to express my warmest thanks to Dr. E. L. Mark, 

 who gave me the facilities of the laboratory, and wlio made 

 possible my trip to Bermuda. 



2. Protozoa and Porifera. 



With any efiort to trace animal pigment back to the blood- 

 system there arises at once a very serious difficulty. Pigmenta- 

 tion as such appears phylogenetically long before the rise of 

 the blood-system. How, then, is it possible to assume that all 

 coloration comes from the blood ? 



Among the Protozoa the only class — with rare exceptions — 

 which contains chromatophores is the Mastigophora (Minchin, 

 1912, p. 13). Here, however, the pigment is probably in every 

 case chlorophyll, or a substance closely allied to chlorophyll. 

 A typical species of chlorophyllogenous protozoa is A r c h e r i n a 

 boltoni, which was described by Lankester (1885). One 

 notable exception to the assumption that all protozoan pig- 

 ments are closely related to chlorophyll is found in Stent or 

 c ae r u 1 e u s , which possesses a blue pigment called by Lan- 

 kester (1873) ' stentorin '. Spectroscopically the absorption 

 bands of this pigment, quite unlike chlorophyll, resemble those 

 of the blue algal pigment, phycocyanin, which, according to 

 Phillips (1911, p. 596), when present even in minute amounts, 

 greatly alters the spectrum of chlorophyll. Consequently 



