Observations on Saprolegniea. 23 



in Fig. 4, PI. IV., and in four hours more the contents of the 

 sporangium are arranged into man}^ spherical bodies (Fig. 5) of 

 about one-fourth the diameter of the sac, and in some cases 

 that I timed they passed from the sporangium is about twen- 

 ty-four hours after the septum was formed. 



Just before escaping the zoospores at the base always take 

 on an oscillating motion, which passes to the zoospores next 

 above and so on to the summit, causing such a pressure that 

 in less than a minute the power is such as to cause a rupturing 

 of the sporangium, which, in normal conditions, always takes 

 place at the summit. The zoospores now pass out, at first very 

 rapidly, so that it is impossible to count them, but when about 

 one-half out they become more quiet, seldom losing their 

 motion however, until all have passed from the sac. In pass- 

 ing out they are very much constricted, so that if any lose 

 their power of motion before they have escaped, it is impos- 

 sible for them to pass out. Having passed from the sporangium, 

 which was emptied in one minute, they swarmed around very 

 lively for nearly four minutes, at the end of which time they 

 settled down, lost their cilia and became spherical. (Fig. 9.) 

 At the end of one hour and thirty minutes they had germinated 

 (Fig. 10.) and one hour later growth had proceeded to the ex- 

 tent shown in Fig. 7. Except at the tip, the growing filament 

 was perfectly clear. In another case zoospores given off at 

 12.30 o'clock were found germinated at 3.30, at which time 

 they underwent a very singular change. A swelling appeared 

 on the zoospore similar to that seen in germination, but, 

 instead of elongating, it gradually enlarged into a spherical 

 body, at the same time the contents of another cell shrank 

 proportionately from the opposite side, and in forty seconds 

 there was nothing left of the old zoospore but a delicate trans- 

 parent sac. This new body took on an oscillating motion and in 

 two minutes separated itself from the old sac, taking on an irreg- 

 ular form,' after which it swam around for three minutes, 

 then settled down and became spherical, the larger granules 

 settling to one side. Germination took place twenty-five min- 

 utes later. The same change took place in all the zoospores 

 noted from this sporangium, and the same was seen in other 

 cases, but as a rule it does not occur. The sporangium was 



' I have since found this change spoken of by M. Cornu, who also says that this new body is 

 provided with two cilia, but in these specimens I saw none. 



