IV THE COLOURS AND PIGMENTS OF PROTOZOA 77 



As to the pigment itself, according to Johnson 

 it normally varies in tone from bright sky-blue to 

 pale sea-green or even dull bluish-gray, but if the 

 organisms are kept under unfavourable conditions 

 it becomes reduced in quantity and changes to 

 a yellowish-brown colour. This change always 

 occurred when the Stentors were artificially divided, 

 and Johnson never found the blue colour to be 

 regained when once lost — a curious fact (the 

 statement, of course, refers to forms kept in con- 

 finement). Individuals are sometimes found which 

 are almost devoid of pigment. Schuberg observed 

 a fact confirmed by Johnson that the pigment is 

 thrown out of the living Stentors apparently in the 

 same way as that in which faecal matter is got 

 rid of; the pigment tends especially to accumulate 

 near the point of attachment in forms which have 

 remained long in one place. 



The blue pigment is extremely stable, not being 

 dissolved by alcohol, ether, etc., nor attacked by 

 acids or alkalies. 



Another Protozoan {Nassuld) also contains a 

 blue pigment which is probably derived from the 

 Oscillatoria of the food. 



Another beautiful violet pigment, apparently of 

 unknown characters, is described by Dr. O. Nusslin 

 in a Protozoan {Zoonomyxa violaced) found in the 

 Herrenwieser Lake. This organism has its proto- 

 plasm filled with numerous small violet vacuoles, 

 sufficiently abundant to colour the whole organism 

 violet. The pigment has a superficial resemblance 

 to one described by Greeff in Amphizonella violacea, 

 but in that form the pigment is granular, while here 



