6 On Peridinium Cypripedium and Urocentrum Turbo. 
figures it as having an ovate three-cornered body, “ corpore ovato 
triquetro,” and states that the stylus or tail equals one-third the 
length of the body, “stilo tertiam corporis partem cequante ;” 
whereas the American Peridinium has an “ oblique pyriform 
outline,” and the so-called flagellum is at least half as long as 
the body. 
Between the statements of Ehrenberg and Claparéde there is 
such a marked discrepancy that I am pretty well convinced that 
the testimony of the latter cannot by any means be used as an 
adjunct to the description of the former; for whilst Ehrenberg 
speaks of the “corpore non ciliato, fronte cilis coronata,” 
Claparéde states (p. 76), in the first place, that there are no 
other organs than the buccal cirri, but that (p. 185) “it 1s the 
inferior part of the [transverse median] furrow that carries the 
buccal cirri ;”” and secondly, that “ the mouth is not placed where 
Ehrenberg figures it [i e. at the anterior edge of the ventral 
plane], but is lodged in the transverse median furrow which 
that author represents.” 
Supposing, now, the animal of Ehrenberg to be the same as 
that of Claparéde, and the one described by me likewise identical 
with the former, then we must believe that Claparede has com- 
mifted a great oversight in not seeing the most prominent and 
conspicuous cilia, in the region of the anterior annular furrow, 
as described by me, and which, in this assumed case, are in a 
corresponding position with the vibrating cilia-crown about the 
anterior, flat, frontal plane (“um die vordere flache Stirnflaiche 
einem wirbelnden Wimperkranz”’) which Ehrenberg describes. 
It hardly seems possible that Claparéde should have detected 
the smaller cilia in the median transverse furrow and overlooked 
the larger and more conspicuous ones, whilst Ehrenberg, with 
his far less powerful lenses, appeared to find no difficulty in 
making out the latter. It seems therefore much more plausible 
that the Urocentrum of Ehrenberg is not the same as that of 
Claparéde, and certainly more likely that the latter should have 
failed to appreciate the value of the observations of the former 
upon the anterior cilia-crown than that he should have over- 
looked it were it really present. 
I scarcely need add, therefore, that I am at least equally con- 
fident, if not fully satisfied, that Peridinium Cypripedium is not 
the same as the Urocentrum of Claparede. 
Cambridge, Mass., May 12, 1866. 
