OBSERVATIONS ON THE GENUS PYTHIUM. 499 



rangium was formerly attached to the parent hraneh. At 

 1 o'clock the beak was much longer (fig. 13, b) and the vacu- 

 oles had entirely disappeared; and at 2 p.m. (fig. 13, c) the 

 whole contents had become evacuated as zoospores, leaving 

 the empty beak and case behind. Fig. 14 gives the results of 

 the examination of another example. The ripe /oosporan- 

 gium presented at 4,30 p.m. the appearance shown in fig. 14, a. 

 At 5 5 p.m. the beak was considerably advanced in develop- 

 ment {b). Soon afterwards the motion of the protoplasm was 

 much more evident, and a peculiar stage was passed through, 

 during which the contents partially divided up and again 

 became granular. At 5.25 p.m. the soft end of the beak gave 

 way, apparently to the pressure from within, and the contents 

 flowed out (fig. 14, c) and immediately became divided up into 

 five actively amoeboid masses, which were soon afterwards 

 further separated in the jelly-like envelope; during the next 

 few minutes each acquired a vacuole and two lateral cilia, and 

 at 5.35 (fig. 14, d) were transformed into five rapidly struggling 

 zoospores, moving in jerks, and changing the form of their 

 amoeba-like bodies continuously. At 5.38 they were all free, 

 escaping rapidly from their mucous prison and swimming about 

 as reniform zoospores of the well-known type. 



Before proceeding to describe the other mode of behaviour of 

 these bodies, I may record the observations registered in 

 fig. 16, on the development of the zoospore itself. The 

 /oosporangium in this case was in the condition shown at 

 fig. 16, « at 5 o'clock, having lain for several hours in fresh 

 water. As there shown, the granular contents had become 

 excavated by vacuoles of various sizes, and a prominent, firm 

 beak was developed. The vacuoles had not been long formed 

 when the figure was drawn, and were rapidly changing their 

 sizes, numbers, and position, as the granular protoplasm became 

 churned-up, so to speak. The rate at which the changes were 

 proceeding at this period may be estimated by comparing 

 fig. 16, a, b and c, all of which were registered within five 

 minutes. 1 The condition shown in b was reached in three 



1 The plan I pursued in making these drawings was chosen after several 



