204 University of California Publications in Zoology [VOL. 19 



C. A. Kofoid for his suggestive interpretations and criticisms, both 

 constructive and destructive, and for the determination of the extra- 

 nuclear division center. 



MATERIAL AND TECHNIQUE 



Plentiful material was found in an aquarium where goldfish 

 were kept. These were obtained from the Yorizuya Company, who 

 represent the Nippon Gold Fish Company and import direct from 

 Japan. In no other cultures have I found Collodictyon. Since it has 

 only been noted from India and central Europe, it is possible that it 

 is not native to California, and may have been introduced with the 

 importation of goldfish from Asia or Hawaii. On the voyage from 

 Japan, however, the barrels in which the fish are contained are 

 emptied and fresh water added at Hawaii and also at the wharf in 

 San Francisco. It would be easy for the flagellates to be brought 

 through notwithstanding this change of water, either by being trans- 

 ferred with the fish, with water plants which are brought in the same 

 aquaria, or by clinging to the moist sides of the containers (barrels). 

 Thus, though there is a possibility that Collodictyon has been intro- 

 duced into California, the cosmopolitan distribution of Protozoa makes 

 this highly improbable, and this genus may be regarded as indigenous. 



These forms have persisted and usually have been dominant in an 

 aquarium 26.5 x 60 x 20 cm., the bottom of which is covered with sand 

 to a depth of about an inch, in which Ulothrix has grown in quantities 

 and to which I have added Lemna, Ranunculus, and Myriophyllum. 

 At least one goldfish has been present all the time, at times two and 

 four. These fish have fed freely on the plant life of the aquarium, 

 making it necessary to replenish all higher plants and on more than 

 one occasion, the algae, although the aquarium has been sufficiently 

 well balanced for one fish to survive since January, 1916. The aqua- 

 rium has been placed outside a window with southern exposure, partly 

 protected by glass plate and wooden cover. The variations of tem- 

 perature for the year have been from about 28 F to 92 F. Con- 

 siderable variation of temperature from the heat of the direct rays of 

 the sun at mid-day to the cool nights failed to destroy the culture. 

 Since the cooler weather of last December Collodictyon has been sup- 

 planted at intervals by a dinoflagellate, Peridinium penardii Lemm., 

 as the dominant organism, the latter seeming to be favored by the 

 cooler weather. On one occasion the aquarium froze over during the 



