168 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



The first evident sign of a spore stage is when the filaments, having reached a 

 certain length, become more or less clavate at their free ends. It is then noticed that 

 the protoplasm is much more abundant here. A constant circulation of grannies in 

 the protoplasm is going ou, and the small nuclei are seen gradually moving along the 

 cell wall toward the end of the filament. A band of protoplasm, free from grannies, 

 is next formed at .he lower end of the clavate part of the thread, and across the 

 lower side of this is rapidly developed a horizontal septum shutting off the club- 

 shaped part of the hypha. Within this cell is now seen a shifting of protoplasm, 

 with an appearance and disappearance of vacuoles. The septum has in the mean- 

 time become slightly convex downward, and the hyaline band has again become gran- 

 ular. When this shifting movement has continued for some time, the protoplasm is 

 seen to form gradually into spore-like masses thickly crowded together and lining the 

 cell wall. These become less distinct at times, and at last seem to lose their identity 

 entirely. In the meantime a short papilla has been forming on the end of the cell, 

 and the septum becomes convex upward. The spores again become distinct, though 

 crowded closely together, and suddenly those near the papilla are seen to be forced 

 into it and pressed against the wall, which is quickly ruptured. The zoospores now 

 rush out through the ruptured place, and soon swim out of sight; but all may not 

 succeed in escaping from the zoosporangium. 



Their form is ovate to oblong-ovate, with two cilia on the smaller hyaline 

 end. By the lashing of these they keep up a rapid movement for some five or ten 

 minutes, when, in the majority of cases, this ciliary motion gradually lessens and 

 finally stops. Assuming now a spherical shape, the spore loses its cilia and secretes a 

 cell wall. In some cases, however, those zoospores which failed to escape from the 

 zoosporangium were seen to move around for nearly an hour before becoming quiet. 

 These spores while motile are without a proper cell wall, and frequently slightly change 

 their shape. In the meantime the septum at the bottom of the zoosporangium becomes 

 greatly convex upward, and a new growth of the filament takes place within the wall 

 of the empty zoosporangiuin, this in time giving rise to another zoosporangium. 



The zoospores, after a short period of rest, are said to go through a second swarm- 

 ing, and then become stationary, as before. Soon after this second swarming the true 

 germination of the spore takes place. This begins with a slight distention of the 

 spore on one side. This distended part gradually becomes elongated, and is then seen 

 as a germ tube proceeding from the side of the spore. The growth of this tube is very 

 rapid, although less so than that of the filaments of the fungus, being slowest while 

 the tube is getting a good start and, at the last, when the protoplasm is about 

 exhausted, but otherwise nearly uniform. The germ-tube tends to be bent or flexu- 

 ous rather than perfectly straight. After it has made a slight growth vacuoles or 

 rifts begin to appear in the protoplasm of the spore. These widen as the contents are 

 gradually drawn into the tube, until the spore is entirely emptied. One germ -tube 

 was observed that had reached a length of 145 microns before the germination had 

 entirely ceased. These germ-tubes are without septa or branches, and each spore 

 forms but one such tube. Spores germinated in water made a growth of the germ- 

 tube equal to about 1 micron each minute during the time observed. The rate of growth 

 of three different spores was respectively as follows : 45 /< in 45 minutes j 15 yu in 20 

 minutes j and 42 fx in 32 minutes. 



