276 H. MAESHALL WARD. 



and the above method (or that of suspending a small speci- 

 men grown on a fly's leg in a drop of water under a cover-slip) 

 is advantageous in many ways. I may add, however, that with 

 care observations may be made with Zeiss E without any 

 cover-slip at all on favorably situated portions. 



The Zoosporangium is simply the terminal portion of 

 a branch spreading freely in the water ; this becomes slightly 

 dilated into a club-shaped body, into which very granular pro- 

 toplasm collects, giving the young zoosporange a dull grey 

 appearance, easily detected with a good hand lens. The apex of 

 this body remains blunt, and the walls are not thickened 

 During the course of about an hour after the protoplasm has 

 slowly accumulated, the following changes occur: — (1) A thin 

 septum becomes formed at the base of the dilated portion, 

 separating its dark grey, non-vacuolated, coarsely granular 

 protoplasm from the more sparsely granular, vacuolated contents 

 of the rest of the branch ; and (2) an aggregation of the con- 

 tents of the zoosporange around numerous centres takes place. 

 To take an instance actually observed (PI. XXIf, fig. 1). The 

 gradual swelling and filling of the zoosporange (a) was completed 

 by about 11 a.m. ; at 11.15 (b) the septum had become formed, 

 and the protoplasmic contents were already denser and showing 

 signs of aggregation at many centres; at 11.45 this had pro- 

 ceeded so far that no doubt of the existence of a multitude of 

 small semi-detached masses could be entertained (fig. 1 c). 



And now followed a most remarkable phenomenon. At 

 about twelve o'clock the appearance shown at c was replaced 

 by one similar to that shown at b ; this had occurred in many 

 previous examples, and puzzled me exceedingly, and I was 

 accordingly prepared to watch the exact sequence of events in 

 this instance. The protoplasm at 11.50 was distinctly divided 

 up into a large number of nearly globular independent masses, 

 slightly compressing one another. No membrane could be de- 

 tected around any of these, though, as subsequent investiga- 

 tions showed, a sort of watery-looking, clear boundary stood 

 between the masses. At one to two minutes after 12 the 

 masses and their clear boundaries became indistinguishable ; 



