90 University of California Publications in Zoology [VOL. 13 



haematoxylin stain, I am unable to say. One is here working at the 

 limit of microscopical vision and the possibility of error in interpre- 

 tation is not excluded as a third contingency. 



2. Diplodinium ecaudatum forma caudatum Fiorentini 



PI. 5, fig. 6 



Diplodinium caudatum Fiorentini (1889), pp. 15, 16, pi. 3, fig. 2. 

 Diplodinium rostratum, Fiorentini (1889), p. 16, pi. 3, fig. 3. 

 Diplodinium rostratum, Eberlein (1895), pp. 262-263, pi. 18, fig. 18. 



The forma caudatum of the species Diplodinium ecaudatum was 

 first described and figured by Fiorentini (1889). Although he gives 

 only a very brief and entirely inadequate description of the shape 

 and structure of the body and fails to interpret correctly the things 

 which he saw, and although his drawing is not only crude and inade- 

 quate, but also in some respects absolutely erroneous, still he was the 

 first to describe this form and in many ways his drawing is a better 

 representation of the living animal than is that of Eberlein (1895). 

 It is not desired to criticize too harshly the work of either Fiorentini 

 or Eberlein, but merely to point out the fact that the previous work 

 on this form is entirely inadequate. 



After a careful study of the description and figure of D. rostratum 

 by Fiorentini (1889) it seems certain, as has already been pointed 

 out (p. 51), that the individual which Fiorentini describes as D. ros- 

 tratum is nothing more than D. e. forma caudatum observed shortly 

 after division. 



If one were to draw the anterior portion of a dividing individual 

 of D. ecaudatum forma caudatum in which the division was just com- 

 pleted, the result would resemble Fiorentini 's figure of D. rostratum. 

 In such a case the relatively great width of body, the blunt, rpunded- 

 off posterior end, and the short, stumpy tail would all be accounted 

 for. Even the two small, unequal contractile vacuoles, placed close 

 together, are characteristic of the recently divided individual. If 

 this interpretation is correct, then D. rostratum falls into the synonymy 

 of D. e. forma caudatum. 



Eberlein 's (1895, pp. 262-263) description of Diplodinium ros- 

 tratum Fiorentini covers also the form which Fiorentini describes as 

 Diplodinium caudatum. To quote: "Ferner ist das von dem gleichen 

 Forscher in seiner Abhandlung (1889) auf Taf. Ill, fig. 2, abgebildete 

 und das Diplodinium caudatum Fiorentini beschriebene Thier zwei- 

 felsohne mit dieser Form 'identisch' und tauscht nur einzelne Ver- 



