432 MARCUS M. HARTOG. 



constituted later on, and that herein is the true essence of the 

 homogeneous stage. i Probably, also, the stage of shifting 

 vacuoles is due to the reconstitution of these resistant layers. 



As to the nuclei which exist in the first stage (of preliminary 

 division),^ Biisgen adduces facts which make it probable that 

 nuclear multiplication takes place during the homogeneous 

 stage. The observation of the nuclei is extremely difficult, 

 and I am still seeking a satisfactory technique for the pursuit 

 and elucidation of this division of the subject. 



II. The Liberation of the Zoospores. 



As already stated, the emission of the zoospores has been 

 ascribed by previous observers to the secretion of an expulsive 

 matter in the sporauge, which swells up in the water to expel 

 them. Now, if such a substance existed it should be visible 

 by some difference of refrangibility or staining in the spo- 

 range or outside. But there is no matter lining the sporangial 

 wall that will stain in any reagent, or refract differently to 

 the water of the preparation. I have tried aniline dyes, hse- 

 matoxylin, picrocarmine, before and after fixation by osmic 

 acid, picric acid, absolute alcohol, and obtained no sign of its 

 existence. There is no streakiness in the water (even on 

 staining) at the emptying of the sporange. In this case we 

 may fairly say, " De non apparentibus et de non exsistentibus 

 eadem est ratio.^^ But if we follow the process of expulsion 

 fully and minutely, we shall be led to another explanation, 

 admissible as involving a vera causa: acceptable, as cover- 

 ing all the facts. To understand it we must review in detail 

 the processes of the definitive separation and emission of the 

 zoospores. 



The protoplasm which hitherto filled the beak usually forms 



' I must here note that in Leptomitus the first lines of demarcation 

 never wholly disappear ; the homogeneity is never absolute. 



2 Whence Marshall Ward's identification of the lines as nuclear plates is 

 inadmissible. His words are rather ambiguous, "A phenomenon of nuclear 

 division in which the cell plate first formed becomes used up again" (1. c, 

 p. 2S6). 



