REPRODUCTION 419 
only the Alge but the Fungi afford examples of the 
development of such cells, conspicuous among them being 
Saprolegnia and its allies (fig. 165). These free-swimming 
protoplasts are known as zoospores or zoogonidia. Each 
on coming to rest clothes itself with a cell-wall, and can 
develop into a plant exactly like the one from which it 
arose. ‘These zoogonidia are developed by the protoplasm 
of a single cell dividing up into a variable but often large 
number of separate protoplasts, the process being known as 
iY 
5 2 
Fic. 166.—Ca:nocyTe or Mucor, BEARING A Fic. 167.—Asci. a, MIXED 
GonrpanciuM, k. THIS IS MORE HIGHLY WITH BARREN HAIRS OR 
MAGNIFIED IN THE FIGURE TO THE RIGHT. PARAPHYSES €, f; FROM HyY- 
one MENIAL E bel. 
m, columella; 2, gonidia. a LAYER oF Pesiza. 
free cell formation. Hach protoplast possesses a nucleus 
derived from the original nucleus of the cell in which the 
formation takes place, in the manner already alluded to. 
In most cases where these reproductive cells are met 
with they have not so simple a structure as those so far 
described, but each is furnished with a cell-wall. They 
are commonly called spores or gonidia, and arise in differ- 
ent ways upon the plant, often, or indeed generally, being 
developed in or on special organs, known as sporangia or 
gonidangia. 
