502 S. O. MAST 



Euglena minima 



Euglena minima appeared at Nela Park in a pool containing 

 much decaying grass. Here the organisms were collected in 

 great abundance but they did not orient precisely enough to 

 make it possible to obtain accurate results. A number of dif- 

 ferent tests was made and although the results obtained were 

 very indefinite they seem to indicate that the stimulating effi- 

 ciency of the different wave-lengths is the same as it is for the 

 other species of Euglena tested (table 15). 



The results of one series of these tests may be found in table 

 9. In this series the ocular slit was opened to 2.5 mm. so as to 

 increase the illumination and the accuracy of orientation. This 

 resulted in a very impure spectrum and consequently greatly 

 reduced the value for comparative work of the readings. 



Phacus triqueter 



A considerable number of specimens of Phacus triqueter was 

 found in liquid material collected in a pig-yard in Michigan near 

 Ann Arbor (August 17). These specimens were fairly strongly 

 negative, while most of the other organisms in the solution were 

 either indifferent to light or positive. Thus it was possible in 

 the course of a few days to isolate a sufficient number of them 

 to make some fairly satisfactory readings in the spectrum. The 

 results of these readings are given in table 6. This table shows 

 that the relation between wave-length and stimulating effi- 

 ciency in this form is practically the same as it is in Euglena 

 (table 15). 



Trachelomonas euchlora 



On July 1 a small pool was discovered on an abandoned clay 

 road in an open woods about half a mile south of the laboratory. 

 The water in the pool was distinctly yellowish-green, due almost 

 entirely to the presence of Trachelomonas euchlora. In the 

 laboratory the specimens collected were found to be very strongly 

 negative, but unfortunately they were not tested in the spec- 

 trum until July 29, when those in the laboratory, though still 

 fairly numerous, responded much less precisely and those in the 



