ACriLYA. 



[ 8 ] 



ACHLYA. 



clearly defined outlines, but are stiU con- 

 nected together by a gelatinous substance in 

 ■wliicb they are completely imbedded. These 

 secondary cells then become retracted from 

 the walls, and accumulate in a dense, rather 

 confused looking mass in the centre of the 

 sporange ; endosmose of water through the 

 now bare ceUidose wall of the sporange 

 seems to exert a pressure upon them,and also 

 on the wall itself, whicli finally bursts at the 

 process or beak mentioned above, and the 

 secondary cells nearest the opening are shot 

 out with some force, the rest following, but 

 gradually more qidetly. There is no inde- 

 pendent motion of the contents, or j erking 

 of the secondary cells, before this emission 

 of the latter ; on the contrary', while in the 



Fig. 1* 



Achlya prolifera, discharging its zonsporps: the lower 

 zoospores treated with iodine ; magnified 400 diameters. 



sporange, they adhere so closely that their 

 shape is scarcely distinguishable, and it is 

 only when the greater portion have escaped 

 that it is iierceived that the pressure had 

 caused them to assume a spindle-shape. As 

 the emission of the secondary ceUs goes on, 

 those escaping first are only removed so far 



as to make room for their successors, and 

 the whole remain adherent together as a 

 globidar mass or " capitidum " seated on the 

 apex of the sporange ; they reassume, more 

 or less completely, the spherical form, by 

 degrees, after they have escaped from the 

 sporange : those w'hich can expand freely 

 become globular; those pressed upon by their 

 fellows become polyhedral. At the time 

 of emission, these secondary cells exhibit a 

 double line at the circumference, which 

 seems to indicate the thickness of the pri- 

 mordial utricle. Soon after the expulsion 

 another deUcate line is detected external to 

 these ; and this indicates a newly produced 

 envelope, which becomes thicker with age, 

 and after a certain time can be 'coloured 

 blue by sulphuric acid and iodine, which 

 demonstrates its composition of cellulose. 

 Application of a strong acid is necessary for 

 this purpose. 



The globular head of secondary cells 

 remains for two or three hours attached 

 upon the summit of the empty, colourless 

 sporange. Then these minute cells emit 

 their contents by a lateral orifice, giving 

 origin, each of them, to a zoospore or active 

 gonidivmi. Neither the motion nor the 

 appearance of cilia follows the expulsion im- 

 mediately, but takes place after the gunidia 

 have increased somewhat in size and ac- 

 quired an ovate form. The duration of the 

 motion lasts from a few seconds to a few 

 minutes, after which the gonidium sinks to 

 rest and begins to germinate. The gonidia 

 possess no cellulose membrane while in 

 motion, but acquire one when they come to 

 rest and germinate. The cilia are two, and 

 arise fi'om the point which first emerged 

 from the parent vesicle, and which at all 

 periods exhibited a lighter tint, indicating 

 a vacuole in the protoplasmic mass. If 

 the expulsion of the gonidia is prevented 

 (as occurs sometimes when the plant is kept 

 under the pressure of a glass slide, in too 

 httle water, in microscopic investigation 

 of it), the gonidia germinate within their 

 ceU-membraues, wliich, instead of dis- 

 charging active zoospores, emit germinating 

 prolongations, just like those issuing from 

 the single germinating gomdia. These spread 

 out here in all directions from the globular 

 capitvlmn, still seated on the end of the 

 sporange. 



During the formation of these sporanges 

 and the gonidia, after the septum has been 

 completed, the tube sends out lateral 

 branches from just below it, which some- 



