1887] The Significance of Sex. 35 
minute as to be visible, only as a cloud of refringent points, 
under a magnifying power of four thousand diameters.. (See 
Roy. Micr. Journ., April, 1886.) Dallinger saw these points grow 
until they attained the size of nuclei, then there was differentiated 
a narrow zone, which increased in width around the nucleus and 
formed the cell. At the time this zone first appeared the hither- 
to homogeneous nucleus differentiated microsomata within it. 
(See Fig. 98, a—e.) As the flagellates seem to be the lowest of the 
forms of life in which all other groups converge, we should ex- 
pect here the most primitive methods of reproduction. This 
mode of spore formation follows conjugation: the nucleus spreads 
by a sort of dissolution through the plasma as in the case of the 
_ cyst forms. When the latter is broken, these spores imbedded 
in a plasma fill it’ Have we not here a direct reduction to the 
gemmule condition, each gemmule being given a chance to start 
a new cell, z.e. a gemmule colony ? 
©- From the simple modes indicated above, we can easily derive 
the methods of reproduction obtaining among the Protozoa. If 
the whole or a part of the nucleus segments into spores which 
remain in a “brood pouch” in the cell-body, and are liberated 
as motile young, we get the “ germ balls” of Stein. Compare 
Figs. 22, d, 23, 29, 30, 32, 33, 34. The structures here indicated 
are similar, but in many cases these nucleated bodies simply rep- 
resent a stage of development or of kinesis of the nucleus, and 
are not liberated as spores. Bütschli is inclined to disbelieve in 
this mode of reproduction, but it hardly seems as if his objections 
sufficiently disprove the evidence we have of its existence. 
` If the chromatin, instead of remaining uniformly distributed in 
the nucleus, gathers into a particular body, which sustains the 
relation of a nucleus to the old nucleus, we get a nucleolus. 
This is a structure very generally found, especially in highly 
developed cells. The nucleolus is to be conceived as the 
primary body and the nucleus as secondary. Before the nucleus 
can divide the nucleolus must divide; but here we may get multi- 
nucleolated nuclei by the multiplication of the latter, while the 
former remains undivided. . The general law of cell-life seems to 
to conserve in the centre of protoplasmic bodies a supply of 
undifferentiated or primary substance (the zdiop/asm), and to sur- 
round this by concentric structures that protect it, and serve as 
organs of relation to the external world. The external envelopes 
