48 Prot. 
XVIII. PROTOZOA. 
Monas multiplies sexually at 20° C., Greeley (147).—“ Conjugation” 
described in Trypanosoma brucei , Bradford & Plimmer (40). 
Conjugation in:— Bursaria truncatella and Stylonichia pustulata ; in 
the former a large number of micronuclei are formed in each conjugate, of 
which all but one degenerate, Prowazek (300); Euplotes , Prowazek (302). 
—Conjugation in Paramcecium is probably necessary in order to supply 
one conjugant with traces of chemicals the other lacks, and so sustain the 
ferment-forming activity, and increase the digestive function, thus pre¬ 
venting physiological degeneration, Calkins (51). 
In Dendrocometes the three micro-nuclei normally present in each 
conjugant each divide; of the resulting six, one forms the sexual 
nucleus, the others degenerating; noteworthy conjugation of the mega- 
nuclei also, and distinct cytoplasmic “mixing,” Hickson & Wadsworth 
(158). 
3. Nuclear changes: mitosis: directive centres, etc. 
Multiplication processes and loose relationship between nuclear and 
protoplasmic division in the Protozoa; origin of centrosomes etc.; the 
conclusion is arrived at that the achromatic nuclear basis or ground- 
substance, centrosomes, and the basal granules of cilia and flagella 
(including the “Geisselwurzel” of Trypanosomes) are analogous formations, 
with one and the same substance for their foundation, and that in all 
cases they act as locomotive or directive centres, which not only govern 
the nucleus and cell-division, but also in some indefinable way exert an 
influence on the motile appendages of the cell; the influence of the 
centrosome on the protoplasm makes possible, by the separation of the 
chromatin from this latter [see ii, b, 2], a change or modification of the 
cytoplasmic network, into a substance agreeing with the nuclear network 
and exercising the same functions: Hertwig (153). 
Nuclear division (teleomitosis) in Amoeba gleichenii quite comparable 
to that in the cells of higher organisms, Dangeard (78). 
After association of the two sporonts in Monocystis , the nuclear mem¬ 
brane ruptures, and a portion of the nucleus passes out into the cyto¬ 
plasm; this becomes the segmentation- or “micro’’-nucleus. Occurrence 
of centrospheres and spindles, Prowazek (303).—A part of the nuclear 
contents in an associated Monocystis is expelled into the cytoplasm, and 
gives rise to the secondary or segmentation nucleus; this divides up by 
successive mitoses, to form the ultimate sporoblast nuclei, Cecconi (56 & 
57).—Curious “halo” or zone round the karyosome in Gregarina cuneata 
and G. polymorpha ; in these, and also in G. steini, the karyosome becomes 
absorbed, either whole or after fragmentation in si,tic, and no part is 
expelled from the nucleus. In sporoblast-formation the nucleus takes on 
a characteristic “flame-shape,” and gives rise quite irregularly to many 
daughter-nuclei—without any obvious karyokinesis, except in the latest 
stages, where a simple mitosis was seen ( G . cuneata ), Berndt (19).— 
Karyokinetic divisions in the formation of the sexual elements in Stylo- 
rhynchus; the karyosomes are retained and fusion of these takes place in 
the copulative act; the attendant centrosomes probably also fuse, Leger 
(215). 
Behaviour of the karyosome during formation of the microgametes in 
Cyclospora caryolytica ; maturation of the macrogametocyte; formation of 
two reduction-nuclei (extremely like polar-body formation), which are 
finally absorbed in the cytoplasm; the microgametes possess at the base 
of the flagella a deeply staining centrosomic corpuscle or “ blepharoplast ” 
recalling that of Trypanosoma and of the male gametes of Stulorhynchus, 
Schaudinn (335). 
Varied behaviour of the karyosome as regards manner of division, time 
of absorption or expulsion, and its relation to maturation processes and 
