Sy ; Vi 
: special M orphology. and C lassification. 251 
Saprolegniez these tubes give way at the end, and inject 
their contents—minute ‘motile bodies scarcely ‘ooz mm. in 
size, the antherozotds—into the oogonium. In the Perono- 
sporeee, on the contrary, the fertilising tubes do not burst, but 
only touch with their apex the oospheres, which then become 
covered with a cell-wall of cellulose, and develope into the. 
unicellular vospores. Closely allied to this is the mode of 
fertilisation in the genus Lryszphe. The antheridium does 
not here put out any fertilising tubes, but only becomes closely 
adpressed to the oogonium ; this latter does not produce a 
simple oospore, but developes into a perzthectum which is 
multicellular and contains the spore-forming sacs. The 
process of Cozjugation in some Mucorini must also be men- 
tioned. An instance of this occurs in RAzzopus nigricans, 
in which, when two filaments come into contact, each puts 
out, in the direction of the other, a cylindrical protuberance 
resembling the filament itself (Fig. 404). These two pro- 
II. Ill. IV, Vi 
1@ 
= 
op \( 
Fic. 404.—Formation of the zygospore of Rhizopus nigricans: 1,-V. successive 
stages of development ; V. s the mature zygospore. (x 60.) 
ei 
tuberances become closely adpressed to one another by 
their ends, and grow into a club-shaped body, in which a 
quantity of protoplasm collects. When both have attained 
a certain size, a single cell, the conjugating cell (c), becomes 
separated at the upper end of each, the partition-wall be- 
tween the two soon disappears, and they unite into a repro- 
