i14 JOURNAL OF SCIENCE. 
appearance of certainty to what is, at the best, only well-founded 
conjecture. 
One point of great interest in regard to several of the 
genera is their excessive variability. Bergh’s object having 
been to make a thorough investigation of the group, and not 
merely to discover new species, he has paid great attention to the 
varieties of each species, and has succeeded in showing, as Car- 
penter, W. K. Parker, and Rupert Jones, did for the foraminifera, 
and Haeckel for sponges, that each species consists of a “‘ form- 
cycle” of individuals, differing so much that the extremes of the 
series would be ranked, without hesitation, as distinct species, if 
the intermediate steps were unknown. 
It is from some such form as Gymnodinium that Bergh con- 
siders the Ciliata to have been derived, the Peritricha (Vorticella, 
&c.) being, according to him, the oldest and least modified sub- 
division of the group. The interesting genus J/esodinium is in 
many ways intermediate between the cilio-flagellata and the 
peritricha. It has an equatorial band of cilia situated in a 
transverse furrow, but it is devoid of a flagellum, and possesses 
a mouth and temporary anus. From the position of the mouth, 
Bergh considers that the anterior pole of a ciliate answers 
to the posterior pole of a cilio-flagellate, or flagellate- 
infusor. 
One theory of more general interest is advanced, namely, 
that the flagellata are the most primitive of Protozoa, and “ forma 
starting point from which the Noctilucz, the Rhizopoda, the 
Cilio-flagellata, and through these the Peritricha, have developed.” 
The main argument for this view is that so many of the Rhizo- 
poda begin life as mastigopods or flagellate forms. One cannot 
but think, however, that this is making too much of embryo- 
logical evidence. A priorz, it entirely seems more likely that a 
flagellum should have arisen as a differentiated pseudopod, than 
that a pseudopod should have arisen as a degenerated flagellum ; 
but the evidence is altogether too scanty for any very consistent 
theory to be built upon it. At present, it seems to me to be 
impossible to say whether the myxopod or the mastigopod 
should be considered as phylogenetically the older ; and I think, 
therefore, that the following scheme, devised for my last year’s 
lectures, expresses the relationships of the groups of Protozoa as 
correctly as the evidence now at our disposal will enable us 
to do :— 
RADIOLARIA, 
FORAMINIFERA Euchitonia, &c. CILIATAS 
a 
TENTACULIFERA 
LOBOSA HELIOZOA 
(Arcella, &c.) | Actinomonas © 
Lieberkiihnia yt CIL1O-FLAGELLATA 
PROTOPLASTA — Mastigamoeba — FLAGELLATA 
(Ameeba, &c,) 
GREGARINIDA, 
: 
