12 
MORPHOLOGY OF THE CELL. 
This form of free cell-formation is distinguished from the preceding by the circum- 
stance that the whole protoplasm (^and not a part only) collects round several centres. 
If the whole protop]asm,an its contraction, were to form only otie mass, which some- 
times happens, the case would be analogous to Rejuvenescence. 
There occurs also in Achlya a variation of this process, when it forms its swarm-cells 
or zoogonidia (Fig. 9). The protoplasm in the club-shaped swollen end of a hypha 
[contains a number of small nuclei which multiply by bipartition] ; it breaks up 
into a large number of small portions (^), [each including a nucleus,] which become 
completely rounded olf {a) after their escape from the cell in which they are produced 
FIG. 8. — Oogonia and antlieridia of Achlya lignicola, growing on FlG. 9. — Cell in which are produced the 
wood in water ; the course of development is indicated by the letters ^ — F, swarm-cells or zoogonidia of an Achlyci 
a the antheridium, b its tube penetrating into the oogonium (x 550). (X 5So)- A one still closed, B one allowing 
the zoogonidia to escape ; beneath it a 
lateral shoot c ; a the zoogonidia just es- 
caped ; b the abandoned membranes of the 
zoogonidia which have already swarmed ; 
€ swarming zoogonidia. 
(£), and then clothe themselves with a delicate membrane, which they abandon {b) 
when their movement commences {e). 
4. Formation of Reproductive Cells by Division of the Mother- Cell. — In 
the protoplasm of a cell new nuclei are formed by division ; round each of these a 
portion of the protoplasm collects and becomes rounded oflf with a greater or less 
amount of contraction, in order to form a new cell; in this manner the entire proto- 
plasm of the mother-cell is completely used up ; its cell-wall alone remains, if it possess 
one, which is not always the case. 
The formation of the spores of Mosses and Vascular Cryptogams, and of the pollen- 
grains of Phanerogams, always takes place by the division of the mother-cell into four 
