MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Methods 



The necessity of Avorkiug to a very large extent with living material, and 

 tlie very limited numbers of individuals to be found of any one species of the 

 group, except Polykrikos schivartzi and Noctiluca milians, have determined 

 the methods employed, and have excluded cytological investigations and any 

 consideration of life histories. 



Promptly upon arrival in the laboratory the plankton was examined in 

 Syracuse dishes imder the low power, and when some representative of the 

 group was detected it was isolated with a fine pipette, placed on a slide under 

 a cover glass and located with the aid of a mechanical stage. When its activ- 

 ities were slowed down it was usually possible to determine its dmiensions by 

 the aid of the camera lucida, or even to get an outline of its more evident 

 structures. Interpretative sketches, color notes, and other details were gen- 

 erally obtained before the rounding up, cytolysis, and death of the organism 

 occurred. It was not always possible to get all the details from one animal, 

 or in some cases to determine all the desirable points in the brief time of 

 observation. This fact explains some of the deficiencies in our accoimts of 

 these interesting animals. 



Colors are recorded in the system of nomenclature of colors proposed by 

 Ridgway (1912). Certain very puzzling difficulties arise in any attempt to use 

 these plates of Ridgway 's with organisms illuminated by transmitted light 

 under the microscope. Changes in the diaphragm, in the focus of the condenser, 

 in the objective used, or even in the source of light, all affect the color values 

 of the object. The same object may have very different color tones under these 

 changing conditions of illumination. Furthermore, it is impossible to find in 

 the Ridgway color samples the exact equivalents of all the colors of the dino- 

 flagellates when thus vicAved. The In'illiance and delicacy of the coloring of 

 these transparent objects is not reproduced in the opaque tones of the color 

 samples. 



The varying refractive indices of the contained fat bodies and other refrac- 

 tive substances, and the color modifications induced by the rapid accumulation 

 of a 2)inkish fluid in a peripheral zone of vacuoles as cytolysis impends, all 

 coml)ine to increase the difficulty of giving a correct interpretation of the color 

 values of these particolored organisms. In view of the reduction in color values 

 due to the amount of light necessary for observation with the higher powers 

 of the microscope and to the color changes diie to approaching death, it is 

 probable that the colors as portrayed in our plates are not exaggerated, and 

 are. in some cases at least, much less brilliant than they are in nature. 



Much aid in the trying process of pursuing these incessantly moving 

 organisms has been secured by the use of the high-power, binociilar microscopes 

 of Leitz and of Bausch and Lomb. These have also proved invalualile in the 

 analysis of the complicated furrows and girdles of this group and in revealing 

 the true contour of the surfaces. 



