No. 3] MORPHOLOGY OF THE STENTORS. 471 



tions mounted in balsam, damar, or glycerine are essential for 

 study of the micronucleus, particularly at times of fission and 

 conjugation. 



II. Systematic and Faunistic. 



The classification of the Stentors has always been difficult, 

 on account of the great variability of most of the species. 

 Consequently, different authorities have held very divergent 

 views as to the number of species. Claparede and Lachmann 

 ('59), for example, relegate the six forms described by Ehren- 

 berg ('38) to two species, while Saville-Kent ('82) increases the 

 number to nine. But the whole question of the specific dis- 

 tinctness of the different forms found in Europe has been so 

 ably and fully discussed by Stein ('67) and his six species ^ 

 have held their own so successfully that I see no occasion 

 to alter his classification. Only one valid species, Stentoj' 

 auricula, Sav. Kent, has been added to the European list since 

 Stein ; for I question very much whether S. Barretti, Barrett, 

 will on further examination prove to be distinct from 5". roeselii ; 

 and the various alleged "new species" of de Fromentel ('74) 

 imperfectly described and too evidently based upon aberrant 

 specimens, no longer hold a place in the system. 



Our American Stentor fauna shows a surprising correspond- 

 ence with that of Europe. With the exception of two marine 

 forms, S. viultifonnis and 5. auricula, every European species 

 has been mentioned as occurring in this country.^ In addition 

 there seem to be two species (5. globator, Stokes ('85), and 

 5. pyriforniis sp. nov.) not found in Europe ; but it must be 

 admitted that neither of these species can be considered as 

 fully established. 5. globator is so aberrant that it might be 

 regarded as based upon abnormal, dwarf specimens of one of 

 the well-known Stentors, especially as the discoverer does not 

 appear to have observed it more than once. While 6". pyri- 

 fonnis is founded upon examination of a very large number of 

 specimens, none of which showed transition to any known 



^ S. polymorpkus, caruleus, roeselii, igneus, niger, and tnultiformis. 

 2 I have never myself seen S. niger; but it is given by Stokes ('88) in his list of 

 American species. 



