No. 3.] MORPHOLOGY OF THE STENTORS. 469 



species or variety found very sparingly or not at all at the 

 others, and only one form, roeselii, has been collected at all four 

 stations. 



Methods. 



The study of Infusoria requires a special technique ; and, as 

 the wonderful results recently obtained by Maupas ('88, '89) 

 forcibly show, an accurate acquaintance with the life-history 

 and habits of the species under investigation is of the utmost 

 importance. One of the most valuable aids in all biological 

 and morphological research upon these organisms is the isola- 

 tion of individuals for continuous study and experiment, — a 

 method exceedingly simple in conception, but, owing to the 

 minuteness of most Infusoria, often far from easy to carry 

 out. This difficulty, however, hardly exists with the Stentors, 

 which rank among the largest of their Class, and are easily 

 visible to the naked eye. 



In collecting, it has been my custom to bring to the labora- 

 tory as much as convenient of the natural surroundings of the 

 Stentors — vegetable debris, sticks, stones, water-weeds, etc. — 

 and a considerable quantity of the water in which the Stentors 

 live. The gathering is put into shallow glass dishes, which are 

 replenished with tap-water from time to time to make up for 

 evaporation. Under these conditions S. ccBmlais will usually 

 thrive and multiply for a week or two ; but owing to the rapid 

 exhaustion of food, and to less well-ascertained causes, one 

 cannot in this way maintain a permanent colony. S. polyiuor- 

 pJuis, S. igneus and 5. pyriformis will usually live in aquaria 

 much longer than the Blue Stentor ; they, however, merely 

 survive as individuals and seem never to increase in number. 



In order to select individuals in fission or other conditions 

 desired for study, I have used a simple contrivance by means 

 of which large numbers can be rapidly reviewed. A slide is 

 prepared by affixing a piece of sheet-wax a millimeter or less 

 in thickness and about an inch square, in which circular holes 

 have been punched. The holes are conveniently made with a 

 cork-borer, and measure 3 mm. in diameter. The wax plate is 

 fused to the slide by very cautious heating of both slide and 



