ON SAPROLBGNI^. 285 



doubtedly true sometimes ; it seemed that in some cases a large 

 block became further cut up into smaller ones. This process 

 proceeded very rapidly, and by 10.53 the zoospore masses (fig. 

 16 d) were finally isolated, and slipped out in the next two or 

 three minutes. The further fate, &c., of the zoospores need 

 not be described in detail; they behave essentially as before. 



Saprolegnia. 



The observations on this genus will be confined to the forms 

 of Saprolegnia ferax (Pringsheim), and the following de- 

 scriptions, &c., will refer particularly to that called S. mon- 

 oica in the sense of the above author. 



Through the kindness of Prof. De Bary, I was enabled to 

 infect "meal-worms" and house-flies with S. monoica, and 

 in two or three days had excellent cultivations floating in 

 abundant water as before. The methods of observation, &c., 

 need not be detailed; they are practically the same as those 

 described for Ac hi y a. 



Fig. IT shows the various stages of development of the zoo- 

 sporangium and zoospores; the segmentation of the proto- 

 plasm takes place as before, and need not be further described. 

 At the completion of the second segmentation, the masses of 

 protoplasm behave in a manner quite diff'erent from those of 

 Achlya, however, since, instead of simply slipping out of the 

 apex of the zoosporangium and then rounding off", they ac- 

 quire two terminal cilia at once, and pass ofl" as actively 

 moving zoospores (fig. IT/). Each zoospore is a top-shaped 

 mass of finely granular protoplasm, with two very long cilia 

 actively waving at its pointed (forward) end, and with a sort of 

 zone of three small vacuoles around its broader part (figs. IT g, 

 19 a). In this condition it moves rapidly from the point of 

 exit, coming to rest (A) after some minutes. With care it is 

 quite possible to watch a zoospore through all its changes. 

 Fig. 19 shows the phases actually seen in the case of a zoospore 

 emitted from the zoosporangium in fig. IT. It became free 

 about 9 a.m., and moved actively for ten minutes, roundin^g off" 

 and losing its cilia and vacuoles in an instant (c f. fig. 19 a, h). 



