112 C. OLIFFORD DOBELL. 
In spite of all the attention which has been bestowed upon 
the Phytomonadina, no one has yet succeeded in demon- 
strating that a nuclear reduction takes place in the gametes 
before conjugation. Hven in Polytoma, which has received 
the attention of so many investigators, no division of the 
gamete nuclei before fusion has been seen (cf. 16, 21, 
29, 36). Prowazek [386] suggests that the formation of 
dwarfs (“ Zwergindividuen”’) may have some significance in 
this respect. In Chlamydomonas also, Dangeard [14] 
finds that no nuclear reduction takes place before conjugation, 
the conjugants having the same number of chromosomes as 
the ordinary individuals. He suggests that reduction occurs 
during germination. 
Now in the lower plants reduction does not seem always to 
occur just before conjugation. For instance, it occurs at the 
beginning, not at the end, of the life-cycle in the Desmidiacere, 
Spirogyra, etc., with the first division of the fertilised 
oosphere. That a similar condition obtains in Polytoma is 
possibly indicated by the fact (observed first by Krassilstschik, 
and since confirmed by Prowazek) that the first division after 
leaving the cyst is into eight, whilst subsequent divisions are 
into four daughter-cells. 
I believe the foregoing facts furnish further evidence of the 
plant affinities of the Phytomonadina, and consequently for 
their sharp demarcation from the rest of the Flagellata. 
Summary or Lire-cycLE OF COPROMONAS SUBTILIS. 
In conclusion I will give a brief synopsis of the life-cycle 
of Copromonas. ‘This can be most easily done by means of 
a diagram (see text-fig. C). Starting with the adult monad, a, 
it will be seen that the life-history comprises two different 
cycles—an asexual (upper cycle, figs. b-d), and a sexual 
(lower cycle, figs. e-l). This latter is intimately connected 
with the formation of resting cysts. During the asexual cycle 
multiplication takes place by means of longitudinal division. 
The organism comes to rest, and the flagellum is drawn in. 
