94 FRESH -WATER ALG^ OF THE UNITED STATES. 



and more capable of solution, and by the time the gonidia are formed it is enlarged 

 and cracked, so that room is afforded them to separate a little distance from one 

 another within the parent cell. Now the movements are said to become more 

 active — a trembling jerking which has been compared to the ebullition of boiling 

 water. There is, however, with this a very slight change of space, and in a very 

 short time the gonidia arrange themselves so as to form a little net within the 

 parent cell, a miniature in all important particulars of the adult hydrodictyon. 

 The primary cell-wall now becomes more and more gelatinous, and soon undergoes 

 complete solution, so that the new frond is set free in its native element. As pre- 

 viously stated, in my investigations I have never seen the peculiar motion above 

 described, the newly formed gonidia simply separating a^d arranging themselves 

 without my being able to perceive any motion, or exactly how they fell into posi- 

 tion. 



It is evident that when the species is multiplied in the way just described, the 

 birth of the new frond is consentaneous with the death of the old cell. But when 

 the hydrodictyon disappear in the fall, it is months before they reappear in the 

 spring. It is, therefore, evident there must be some other method of reproduction. 

 This slow development of new fronds takes place, according to Pringsheim, by 

 means of little motile bodies which he calls " Dauerschwdrmer" which has been 

 translated into English chronispores {statospores. Hicks). M. Braun stated already 

 some years since that sometimes, instead of the hydrodictyon producing the ordi- 

 nary reproductive bodies (macrogonidia), there are formed in the cells much smaller 

 and more active bodies, the microgonidia. The changes which occur in the pro- 

 duction of these are very similar to those already described as happening when 

 the macrogonidia are formed. When the chronispores are once formed, however, 

 they, instead of uniting together escape in a free distinct condition into the water. 

 They are now small ovate bodies, with a large anterior transparent space, to which 

 are attached a pair of cilia, and their life and history, according to Pringsheim, is 

 as follows : For a few hours they move about very actively in the water, and then, 

 dropping their cilia, and acquiring an outer cellulose wall, pass into a quiescent 

 stage, in which they closely resemble protococcus granules. They are capable of 

 living in this state for a long time, if kept in water. They can also endure desic- 

 cation if the light be excluded during the process, but, if it be present, they wither 

 and die, and cannot be revivified. 



After a longer or shorter period, but never shorter than three months, according 

 to Pringsheim, they recommence their life, provided they be in water. For four 

 or five months after this the chief change consists simply in an increase in size. 

 The dark-green protoplasm is arranged around the exterior of the cell, within are 

 the more fluid colorless contents, the whole body still looking like a protococcus 

 cell. After a size of about ^ mm. is attained, the endochrome divides succes- 

 sively into several portions. The external layers of the surrounding wall now 

 give way in some spot and allow the inner layers to protrude and form a sort of 

 hernial sac, into which the several endochrome masses soon pass, at the same time 

 assuming the well-known characters of true zoospores. From two to five of these 



