102 'Journal of Comparative Neurology and Psychology. 



smaller ones, especially such as were still within the mother colo- 

 nies, appeared quite normal in color. Intense light evidently 

 causes some change in the chlorophyl. 



The specimens used in the experiments performed at Harvard 

 University were collected in various small ponds located some 

 little distance west of Cambridge. Some of these ponds are arti- 

 ficial, having formed in clay pits; others are apparently natural, 

 being located in low, swampy land. All of the ponds contained 

 numerous aquatic plants, and the water in them was stagnant 

 but clear and not foul. The material used in the work done at 

 Hope College was collected in ponds connected with a very slug- 

 gish river which runs through a marsh directly north of the city 

 of Holland. Colonies of Volvox were found sparsely scattered 

 here and there along almost the entire shore line of nearly all the 

 ponds. In a few spots, however, they were so numerous that the 

 water appeared green, and in these places they could readily be 

 collected in great numbers. 



There are two well defined species of Volvox, globator and 

 aureus (Ehrenberg = minor Stein). In the ponds near Cam- 

 bridge practically all the colonies belonged to the species globator; 

 but in the ponds north of Holland the two species were found about 

 equal in number. They were usually found intermingled, but in 

 a few places I found only globator and in one place nothing but 

 minor. 



After colonies of Volvox have been in the laboratory from 12 to 

 24 hours they become inactive, and no longer respond readily to 

 stimuli, and are therefore not satisfactory for experimental work. 

 This makes it necessary to collect frequently. An abundance 

 of material close at hand is consequently almost a requisite for 

 experimental work on this form. In the following experiments, 

 the specimens usually were collected early in the morning and 

 used the same day. 



3. STRUCTURE. 



Since the discovery of Volvox by Leeuwenhoek nearly every 

 naturalist has had something to do with the study of this exceed- 

 ingly interesting organism. Most of these investigators laid great- 

 est stress on the structure, but in spite of all this work there are still 

 two questions with regard to structure, concerning which there 

 is some doubt. One is the location of the eye-spot with reference 



