REPRODUCTION IN LOWER PLANT LIFE. 107 
e separately from its parent-cell, or the septa become 
absorbed and all the zoospores escape successively through 
a common ostiole at the apex. Some species of Pheo- 
spore possess both kinds of sporange, while in others only 
one or the other kind has at present been detected. There 
1s In some cases a further differentiation, in the two kinds 
of sporange being always produced on different individuals ; 
or, when borne on the same individual, they mature at 
different times. No difference is observable in size or 
form between the swarm-cells produced in the two kinds 
of sporange ; but those produced in the unilocular sporan- 
ges appear to be in all cases non-sexual zoospores, ger- 
minating directly into a new individual, while those from 
the multilocular sporanges are in some instances Zz0o- 
gametes with sexual functions. In Ketocarpus siliculosus 
(fig. 9), a not uncommon seaweed of our coasts, the 
multilocular sporanges present the first rudimentary 
indication of a sexual differentiation. Some of these, 
after a very short period of swarming, become fixed to a 
solid substance by the apex of that one of the two flagels 
which is directed in front in the swarming movement. 
Both flagels gradually disappear, the gradual contraction 
of the anterior one causing the protoplasmic body of the 
swarm-cell to become closely attached to the solid sub- 
stance. During this period it appears to exercise an 
attractive force on other swarm-cells which have been 
swarming around it, and, during the very short period 
that it is in a receptive condition, coalescence takes place 
between the female and one of the male zoogametes. The 
impregnated gamete immediately clothes itself with a cell- 
wall, and proceeds to germinate. It should, however, be 
noted that both male and female gametes are capable of 
germination without conjugation, though the resulting 
new individuals are then always weakly, and soon perish. 
