126 ROMANCE OF LOW LIFE AMONGST PLANTS. 



sometimes up to five o'clock in the evening. Tlie 

 swarming, or formation of nets, would seem to depend 

 much on external circumstances. Some days only 

 the large gonidia seem to be at work in the forma- 

 tion of young nets ; on other days, and especially 

 when the weather is dull and rough, the swarmers 

 are produced in unusual numbers, and then there is 

 no net formation. 



When the water-nets disappear in the autumn and 

 seem to leave no trace behind, it is some months 

 before they reappear in the spring, and this in- 

 terval is occupied, according to Pringsheim, by the 

 " swarmers," or, as he calls them, the " chronispores," 

 undergoing a period of rest or, more accurately, of 

 hybernation. After moving about in the water 

 actively for a few hours, they lose their cilia and 

 come to rest ; then they acquire a thicker outer cellu- 

 lose wall and pass into the quiescent stage, in which 

 state they are capable of existing in water for a long 

 time. 



After a period of not less than three months they 

 recommence active life, and for some time after this 

 there is little manifest change, except an increase of 

 size. When they have acquired a diameter equal to 

 one-fortieth of a millimetre the endochrome divides 

 into several portions, the outer layers of the old cell 

 wall give way, and the inner layers protrude like a 

 sac, into which the contents pass and soon acquire all 

 the well-known characters of true zoospores. From 

 two to five of these are developed from each "chroni- 

 spore " or " resting spore." They are ovate, with two 

 cilia, and, upon their escape from the sac, move above 



