8 MARCUS M. HARTOG. 
also of karyogamy—the association of nucleus and cytoplast 
that are strangers to each other. 
We may fairly adopt the view that multiple isogamy, where 
the fusion of the nuclei follows that of the cytoplast, was ori- 
ginally derived from plasmodial formation, and that binary 
isogamy and the higher forms of karyogamy are further stages 
in the upward path. 
In the Acraste#, the individuals produced by fission simply 
ageregate together without fusion before passing into a rest- 
ing state, asa fructification in which their cellular individuality 
is retained. The only explanation I can suggest for this is 
that it indicates the loss of a primitive formation of plasmodia 
at this stage; the Acrasiez would be an apoplasmodial or 
apoplastogamous group, a degenerate offshoot of the Myxomy- 
cetes. 
III. Toe Moves or KARryYOGAMY AS ILLUSTRATED IN 
PROTOPHYTES. 
Undoubtedly the lowest forms of life that present us with cases 
of karyogamy are the FriaceLuatTes; and in the Puyromas- 
ticorops or Green Flagellates we may study its modes from 
isogamy to complete sexual differentiation. From the colonial 
Phytomastigopods we can trace an almost unbroken line up- 
wards past the Thallophytes, which in their asexual reproduc- 
tion so often revert to the lowly Flagellate type; up through 
the Archegoniata to the Gymnosperms and true Flowering 
Plants at the top of the scale. We distinguish the following 
modes of karyogamy:—(1) Isocamy—(a) Evtsecamy, (6) 
Exorsocamy ; (2) Anisocamy ; (3) Hyproogamy ; (4) Oocamy. 
(1) Isocamy.—This is the simplest mode of karyogamy. In 
this process cells exactly similar fuse as gametes, cytoplast to 
cytoplast, nucleus to nucleus; a single nucleated cell, the 
zygote, being the produce. In most cases only two gametes 
unite in binary isogamy; more rarely three or more may 
fuse in multiple isogamy. In many of the Phytomastigo- 
pods, and some of those simple filamentous or thalloid Algz that 
