REPRODUCTION 427 
emphasised is that the new individual is developed con- 
tinuously after its origination. There 
is no resting period, such as we find 
in most cases, to mark the behaviour 
of the more specialised reproductive 
cells to be discussed below. 
Apart from cases of vegetative pro- 
pagation of the individual, we meet 
with two other methods of repro- 
duction, both of which involve the 
Fie. 164.—Zoosporz or 
Ulothrix. x 500. 
preparation of special cells set apart for this purpose. The 
first of these is characterised by the fact that each cell so 
produced is able to grow, either at 
once or after a short period of rest; 
into a new plant, which may or may 
not be exactly like the one from 
which the reproductive cell was 
formed. In plants exhibiting the 
simple organisation which we find 
among the seaweeds and the fungi, 
the parent and the offspring are in 
most cases precisely similar. The 
difference in this respect between 
them and plants higher in the scale 
will be discussed a little later. A 
good example of this mode of repro- 
duction, which was probably the 
primitive form, is afforded by the 
common filamentous Alga Ulothria. 
Any protoplast of the filament can 
divide into a number of separate 
pieces, each of ovoid shape with a 
pointed end and furnished there with 
four cilia (fig. 164). These new proto- 
Fie. 165.—Two Goxt- 
pana1a o@ Achlya 
A, closed; B, ruptured, and 
‘allowing the zoogonidia a to 
escape; b, mother-cells of 
the latter, after escape of 
the zoogonidia from them, 
plasts swim about for a time in the water, then come to 
rest, and after a time grow out into new filaments. Not 
only the Alge but the Fungi afford examples of the 
