436 MARCUS M. HARTOG. 



of Juranyi, cited elsewhere by Marshall Ward, that in (Edogo- 

 niura the '^ relatively large antherozooid forces its way through 

 an aperture too small for it to reach the attracting oosphere/' 



The exit is so rapid at first because of the contrast between 

 the external medium and the small amount of liquid within 

 the sporange, vitiated by the close-packed thousands of zoospores, 

 and with its gases slowly changed through the sporaugial wall, 

 and because of the immense number of zoospores, all influenced 

 at once by the stimulus. Later on the contrast is lessened, 

 partly by the exit of so many zoospores, partly by the influx of 

 aerated water from without to occupy the room left by their 

 exit. Only near the very mouth of the sporange is the contrast 

 marked enough to accelerate the pace of the foremost zoospores. 



But when the water is left unaerated there is no difference 

 as regards oxygenation between the inside of the sporange and 

 the surroundings ; the beak may open, but the zoospores, 

 feeling no attraction to without, stay where they are, and the 

 Dictyuchus state is produced; or, if the aeration be imperfect, 

 only some of the zoospores leave the sporange till those within 

 are no longer attracted and remain inside. 



Finally, we may note that this is only one instance of the 

 extraordinary susceptibility of this group to chemical stimuli. 

 Others are well known, such as the growth of the hyphae of 

 germinating zoospores (especially in the Di ctyuchus condi- 

 tion) towards food material, the germination of the oospores 

 only in presence of food material, the growth of the 

 antheridial branches towards the oogonium, &c : 



The following is an abstract of the chief points I claim to 

 have established : 



1. The clear bands of the first stage of the zoosporange are 

 neither cell plates nor nuclear plates, but thinner parts of the 

 protoplasm due to the aggregation of the greater part thereof 

 around distinct centres. 



2. At the homogeneous stage the protoplasm acquires an 

 extreme perviousness to liquid ; this is probably due to the 

 temporary loss of the resistant layers (Hautschicht, vacuolar 

 walls) as continuous layers. 



