rROTOCOCCACE,K. ,37 



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. 



" 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 Hyd/rodictyon 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 develop- 

 ment of new fronds takes place, according to Pringsheim, by means 

 of little motile bodies which he calls Daue?'schwarmer, 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 (macrogonidia), there are 

 formed in the cells much smaller and more active bodies, the micro, 

 gonidia. The changes which occur in the production of these are very 

 similar to those already described as happening when the macro- 

 gonidia are formed. When the chronispores are 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 dessicatiou 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 colourless con- 

 tents, the whole body still looking like a Protococcus cell. After a size 

 of about 4*0 th mm. is attained, the endochrome divides successively 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 bodies are thus produced out of each original 

 microgonidium. They are large, ovate, biciliate, and, generally, soon 

 escaping from the hernial sac, move about actively in the water for a 

 few minutes. Sometimes, however, they settle down within the genera- 

 tive utricle. In either case, after a little time, they become motionless, 

 lose their cilia, and develop into polyhedral cells, which are structurally 

 remarkable for having their angles prolonged into long, horn-like ap- 

 pendages. Under favourable circumstances, at the end of a few days, 

 the bright green endochrome of these undergoes similar changes to 

 those described as presaging the production of the microgonidia, and is 

 finally formed into zoospores, which, in from twenty to forty minutes, 

 unite, within the polyhedron or large cells, into Hydrodictyon, which is 

 finally set free by a solution of the cellulose coat of the polyhedron. The 

 network thus formed differs in no essential way from that which arises 

 in the better known way, except that it is composed of much fewer cells. 

 It is generally a closed sac ; but when the polyhedron, out of which it is 

 developed, is small, it is sometimes merely an open network. Its after- 

 history appears to be identical with that of the ordinary Hydrodictyon 

 frond." Dr. H. G. Wood, " American F. Water Alga" 



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