ZOOSPORES IN THE SAPllOLEGNlEiE. 429 



Cornu in his classical memoir, so that, for this genus, the exis- 

 tence of an expulsive matter would be essential to liberate the 

 zoospores. In Dictyuchus (genus), Saprolegnia, and 

 Leptomitus the processes and stages diflfer only in minor 

 details from the above. 



In July, 1884, I had the opportunity of going over this 

 matter in Strasburg, under the direction of the same illustrious 

 botanist, Prof. A. De Bary, and with the kind help of Dr. 

 Biisgen. I had in hand a species of Saprolegnia which we 

 were unable to determine, as during the intense heat it formed 

 no sexual fruit. I anticipated nothing more than the confir- 

 mation of my predecessors' results, but to my surprise I found 

 an undescribed phenomenon at the homogeneous stage. As 

 soon as it came on, a crowd of bacteria swarmed from all parts 

 to the neighbourhood of the sporange, and executed a vigorous 

 dance there till the conclusion of the stage, when they 

 dispersed. Inferring that some excretion must take place thus 

 to attract the bacteria, I put in the eye-piece micrometer, and 

 found indeed that the sporange narrowed greatly, by as much 

 as one seventh of its previous calibre. This unexpected 

 result set me thinking, and on my return to Cork I took up 

 the study afresh. Here I have only obtained two species : 

 Achlya polyandra, and a form with the constricted hyphse 

 of a Leptomitus, but which seemed to be identical with 

 Saprolegnia Thuretii,^ sent to me recently by Prof. De 

 Bary's kindness. Though these forms were convenient for 

 study and easily cultivated, they just failed to show the marked 

 contraction so interesting in the undetermined Saprolegnia. 

 I now proceed to describe the chief new points I have 

 made out. 



In the Leptomitus form, and in starved sporanges of 

 Achlya, where a narrow layer of parietal protoplasm sur- 

 rounds an immense vacuole, it is easy to study the real signi- 



' I now think I must have contaminated my culture of S. Thuretii with 

 my Leptomitus form, which I heuce regard as distinct, and define thus: 

 Saprolegnia corcagiensis (n. sp.), diplanetica, habitu, constrictiouibus, 

 zoosporangiis que omuiuo Leptomiti iactei, polygauia, oogouiis fenestratis. 



