4 Prof. H. James-Clark on the Affinities of 
centrum is stated to be at the anterior edge of the ventral face : 
“Vig. 1 von der Seite gesehen, Bauchflache rechts mit dem 
Munde am vorderen Rande.” In Peridinium Cypripedium this 
aperture is on the ventral side and about halfway between the 
two ends of the body—a position which it seems to occupy in 
many of the Peridiniza. 
Although I do not use the word spiral in regard to the mouth 
and cesophagus, it can hardly be said that I “mention nothing 
spiral” about them; for I think that the illustrations tell as 
much as the text ; and any one who will inspect my figures 2 & 3 
will see that the position of the mouth in the first, and the trend 
and curve of the cesophagus in the second, are sufficiently indi- 
cative of a spiral arrangement of these parts. The text fully 
bears out this assertion, in the following words (p. 897 ; Annals, 
p- 274):—*The mouth lies altogether within the posterior 
obliquely transverse furrow (pf), and extends from its anterior 
to its posterior edge, trending diagonally across the axial plane 
of the body, from the right, backwards, towards the left ;? and 
on p. 3898 (Annals p. 275), “ From the mouth the cesophagus (@) 
passes obliquely backwards and towards the dorsal region, at 
least halfway through the body, and then terminates rather 
abruptly just before the contractile vesicle, but a little to the 
right side (fig.3@) of the axial plane.” Lest, however, there 
should be any further doubt in regard to my views upon this 
point, [ will state now that the arrangemént of the mouth and 
cesophagus is decidedly spiral, and unequivocally stamps this 
animal as a member of the lxotropic division of Infusoria 
Ciliata. 
As to the systematic position of this Peridinium, its leotropie 
character at once removes it out of the division to which the 
Vorticellina belong; but yet when we see that one of the latter 
family, viz. Trichodina Pediculus, Ehr., has its contractile vesicle 
on the left side of the body, instead of on the right—thus par- 
tially reversing the relationship of the organs as exhibited in 
the other members of that group (see my paper in the Mem. 
Boston Soc. Nat. Hist. vol. 1. 1866), and that it totally lacks 
the protrusile vibratory disk, so eminently characteristic of the 
Vorticellidae—and when, again, we call to mind the ciliated body 
of another Vor ticellidan, viz. Claparéde’s T'richodinopsis, the 
way appears clear for the close approximation to the Vorticellina 
of the totally ciliated Tintinnoidea with their terminal, depressed, 
cyathiform front, bordered by the crown of cilia, which termi- 
nates, according to Claparéde, by passing into the excentric 
mouth: and then, as a succeeding step, it does not seem at all 
improbable that the Peridiniza, judging from the characters of 
P. Cypripedium, should have a not very remote affiliation with 
