478 JOHNSON. [Vol. VIII. 



weather. This concurrence of favorable conditions causes the 

 brook to swarm with all kinds of active aquatic life throughout 

 the winter. I have obtained Blue Stentors at various points 

 along the brook, and in every month from October to June. 

 What becomes of them in summer I have never been able to 

 determine. During July and August, 1890, I made numerous 

 gatherings at many points along the stream, but without the 

 least success. 



The Blue Stentor of this country is undoubtedly identical 

 with the 5. cceruleus of Europe, but those I have obtained 

 certainly much exceed the dimensions commonly given for the 

 European form. Stein states ('67, p. 240) that the present 

 species attains about the same size as 5. polyviorpJuis, the 

 length of which in extension is given as half-a-line ; i. e., rather 

 more than a millimeter. Maupas ('88, p. 230) gives as the 

 "normal size," length 1.176 mm. and diameter .27 mm. In 

 the semi-contracted condition of swimming the Alewife Brook 

 specimens are commonly a millimeter long, while sessile and 

 extended individuals generally attain a length of 2 mm. and a 

 diameter of .476 mm. across the frontal field. Individuals in a 

 state of extreme extension even reach a length of 4 mm. On 

 the other hand, the largest measurement of 5. polyviorpJnis 

 (fully extended) I have ever made was 1.466 mm. by .365 mm. 



Stein remarks (p. 242) that the nodes of the meganucleus of 

 5. ccerideus are usually spindle-shaped, while those of 5. poly- 

 morpJms are oval. I have frequently seen spindle-shaped nodes 

 in the Blue Stentor, but oval nodes are much commoner. 



III. Morphology. 



For the investigation of nearly all subjects relating to the 

 morphology and physiology of the Stentors, S. ccernleiis is by 

 far the most favorable form. It is of large size ; all its 

 structural features are strongly accentuated ; internal parts are 

 readily seen in the living animal ; it is obtainable in large 

 numbers, and multiplies freely in aquaria. These advantages 

 have been recognized by the different workers upon the 

 Infusoria, and the result is that our knowledge of the Stentor 

 type is very largely based upon the study of 5. cceruleus. 



