(>/ Sphseroplea annulina. 85 



When the spores of Sphceroplea are about to germinate, in the 

 first place their contents are metamorphosed, acquiring a pecu- 

 liar granular organization and assuming a colour more brown- 

 red, a lighter circle becoming visible in the middle. The red of 

 the spore is frequently changed into green before germination, 

 the conversion advancing gradually from the borders to the 

 centre. The contents of the qwre next divide, first into two, then 

 into four or eight portions ; these portions break through their 

 double membrane and emerge into the water as free ' swarming- 

 cells.' In the small number of spores which germinated daily 

 out of the enormous quantity present, I never succeeded in 

 catching the moment of the exit, and therefore I do not know 

 how the two coats of the spore are torn ; but the empty mem- 

 branes are often met with, a mere remnant, at most, of un con- 

 sumed contents remaining in them ; I also found spores with 

 undischarged 'swarm-cells' dancing about actively in their inte- 

 rior. The whole process differs from what Pringsheim observed 

 only in so far, that in Bulboch(Ete a long cylindrical germinal 

 filament escapes from the spore, and the contents of that are 

 formed into free ' swarming-cells,' while in Sphaeroplea this ope- 

 ration is completed within the spore itself; but I often met with 

 spores from which the outer stellate membrane had been stripped, 

 and the contents had begun to divide within the inner smooth 

 coat. 



The ^ swarming-cells * (zoospores) which are formed in the 

 interior of the spores of Sphceroplea have an exceedingly elegant 

 shape, which however, like their size and colour, is subject to 

 considerable variation. Ordinarily they are globular or short 

 cylindrical corpuscles j^q to y]-y of a line long, of a splendid 

 carmine or vermilion colour, furnished at one end with a short 

 colourless head from which extend two long cilia. Other swarm- 

 ing- cells are larger and pear- or spindle-shaped; these evidently 

 derive their origin either from a larger fractional part or from 

 larger spores : I met with globular swarming-spores even as much 

 as yIjj of a line in diameter, not inferior in size to the ordinary 

 spores ; and perhaps these might have consisted of the total con- 

 tents of such a spore swarmed out in one mass. Many swarm- 

 ing-cells are of two colours ; the part next the beak red, the rest 

 green ; or a green border surrounds a red centre ; but the colour- 

 less head or beak, with the cilia, is always evident. Their move- 

 ments last for many hours, and exhibit that vigorous, and yet 

 at the same time lazy character which distinguishes for example 

 the swarming-spores of CEidoyonium, and still more those of 

 Chlamidomonas pluvialis, which are similar also in their colour 

 and the number of their cilia. The long pauses which occur 

 from time to time in the movements of these swarming-cells are 



