56 



THE GENUS HYDRODICTYON. 



cellulose wall of the Hydrodictyon cell has been undergoing changes, 

 becoming thicker and softer and more 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 previously stated in my investigations, I 

 have never seen the peculiar motion above described, the newly- 

 formed gonidia simply separating and arranging themselves with- 

 out my being able to perceive any motion, or exactly how they fell 

 into position. 



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 Prings- 

 heim, by means of little motile bodies which he calls Dauerschwar- 

 mer, which has been translated in English Chronispores (statospores, 

 Hicks). M. Braun stated already some years since that, sometimes, 

 instead of the Hydrodictyon producing the ordinary reproductive 

 bodies (macrogonidici) there are formed in the cells much smaller 

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

 in the production 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 with 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 dessication 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, pro- 

 vided 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 colourless contents ; the whole body still looking 



