298 XXII. REPRODUCTION OF AL,GM. 



apex, and evacuates its slimy contents, of which the greater part 

 remains in the surrounding water in the form of colourless vesicles, 

 which slowly disorganise ; but a smaller part hastens away in the 

 form of minute glancing spermatozoids (antherozoids). These 

 actively swarming spermatozoids soon collect in the mass of jelly 

 at the apex of the oogonium. Individuals press forwards to the 

 colourless receptive- spot of the oosphere, and as it were grope 

 around it. In specially favourable cases entrance of such a sper- 

 matozoid into the receptive- spot can be determined. After a short 

 time the fertilised egg (the oospore or zygote) has surrounded 

 itself with a delicate membrane, which is especially clearly visible 

 at the receptive- spot. In the course of some hours the colourless 

 protoplasm of the receptive- spot is distributed in the zygote. 

 Older oospores are densely filled with oil drops, show some 

 brown spots in the interior, and have a firm membrane. 



If a swarming spermatozoid is fixed with iodine, two unequal 

 cilia, unilaterally inserted, and extended in opposite directions,, 

 can be seen attached to it. 



Reproduction in Fucus. The various species of Fucus, or 

 brown sea-weeds, found everywhere round our coasts, can be 

 obtained in fructification nearly the whole year round. If 

 gathered at high tide, when under water, or immediately after 

 the setting in of the ebb, and sent damp, without any other 

 packing, we are pretty certain to be able to observe the phe- 

 nomena of fructification even at places far distant from the sea. 

 The parcel ought to be accompanied by a considerable quantity 

 of sea-water, or a suitable equivalent for this can be made from 

 prepared salts. After receipt, a portion of the plant should be 

 hung up free on a piece of string, the other part laid in sea-water. 

 In about six hours, after the sexual organs have been emptied, 

 the hanging plants can likewise be laid in sea- water ; and, after 

 about six hours, again taken out and hung up, and thus tlie 

 evacuation of new sexual products induced. If the plants which 

 were hung up immediately on arrival have not yielded sexual 

 products, they may be expected from those which were laid in 

 water, if these latter are taken out after about six hours and hung 

 up to dry slowly. In cool weather the plants can stand a journey 

 of even several days duration without injury, and by laying in sea- 

 water periodically will develop normal sexual products for days. 



Fucus platy carpus. To study the structure of the sexual 

 organs, we will choose in the first place the hermaphrodite species r 



