110 PROCEEDINGS OF THE ACADEMY OF [PaRT I 



jumping organ; and why should their function not be the same in 

 Pteridomonasf There is a fact, indeed, which seems to contradict 

 such a theory, — Pteridomonas pulex, which has no such setae, jumps 

 just as well as Pt. scherffeli which possesses setae, but . . . it is 

 not quite certain that Pter-. pulex is unprovided with setae. None 

 have been seen, it is true, but they are so extremely indistinct, in 

 Pter. scherffeli, that during the first days of my observations I had 

 no idea it was not Pter. pulex I had to do with, and only later on 

 the mistake was found.^ 



It is, then, to that aequatorial girdle of setae that I should be 

 disposed today to attribute the jerks of Pteridomonas, but the ques- 

 tion yet remains in doubt. 



When speaking of the anterior crown, we saw that each of its 

 "flagellopodia" is liable to collapse into a small globular body, 

 and that all of these small pearls constitute then a sessile ring around 

 the central flagellum. Now it is rather interesting to notice that 

 this very sort of ring sometimes is found also at the posterior ex- 

 tremity (Plate V, fig. 1). In that particular locality, the Ariana 

 Park, wdiich furnished practically all my material, this posterior 

 crown existed in one out of five individuals, being sometimes well 

 developed, more often more or less reduced in the number of the 

 "pearls", but none of these pearls ever could be seen to develop 

 into a thread; they were always in the retracted state, and very 

 likely were unable to change in any way. 



As to the meaning of that posterior crown of pearls, at first sight 

 it seems that it would indicate the anterior part of a new individual, 

 to be formed by an act of division which must then prove trans- 

 verse. In spite of the fact that a transverse division would be 

 very exceptional in a Flagellate, I was inclined to consider it as 

 very probable here, till meeting one particular specimen which 

 certainly was dividing (Plate V, fig. 3). It was much broader than 

 long, with two flagella, a nucleus elongated transversally to the ver- 

 tical axis of the body, and two posterior threads, each with some 

 pearls around its base. This specimen showed the beginning of a 

 longitudinal division. We must then conclude that the meaning 

 of the posterior crown is not yet understood. 



1 The first description of Pter. pulex is dated 1890. At that time I had at my 

 disposal only a small, student's microscope, and practically the aequatorial setae 

 must have been invisible. Besides, Pter. pulex hardly ever seems to have been 

 studied afterwards. Scherflfel and Lemmermann had Pter. scherffeli under ob- 

 servation, and though some other observers cite Pter. pulex, I do not know of 

 any who studied it. 



