De Bary,^ and Brefeld," a great amount of accurate infor- 

 mation respecting the Saprolegnim has been accumulated of 

 late years. 



They may be defined as a kind of water-moulds, which 

 usually live at the expense of dead and submerged animal 

 and vegetable substances, and are especially common upon 

 dead insects and other invertebrate animals. Their delicate 

 hyphoe form a white cottony fringe to such matters.^ 



A dead fly which has fallen into water is a favourite 

 nidus for Saprolegnia, the hyphse of \yhich radiate from it 

 in all directions, so that the fly appears to be enclosed in a 

 pale white fluff)' ball. Careful examination shows that such 

 a fly represents the soil in which an immense number of the 

 minute Saprolegnics are implanted. One half of each fungus 

 consists of branching hyphse which answer, in a fashion, to 

 the stem and branches of an ordinary plant, and are visible 

 externally; the other half of the fungus corresponds, in the 

 same general way, to the root and rootlets, the hyphae 

 ramifying in the interior of the fly, and the two parts being 

 connected by a portion which traverses the dense cuticle 

 with which a fly's body is coated. 



The stem-hyphse answer exactly in size and structure to the 

 hyphse of the salmon fungus. Moreover, a large number of 

 them terminate in zoosporangia of the same character, which 

 evacuate their zoospores, and are reproduced in the same way. 



Flies, or parts of flies, such as the legs, on which Sajiro- 

 legnice are healthily growing, can be isolated and watched 

 for any needful time under the microscope, so that the whole 

 process of the formation of the zoosporangia and zoospores 

 can be followed step by step. It may then be observed that 

 the simple subcylindrical free end of a hypha enlarges, that 

 protoplasm accumulates in it, and that its cavity, finally, 

 becomes shut off" by a transverse partition from the rest of 

 the hypha, as a zoosporangium, the summit of which is 

 usually slightly conical. The protoplasm is then seen to 

 break up, simultaneously, into from eight or ten to a hundred 

 and fifty zoospores, according to the size of the zoosporan- 

 gium. The apex of the latter then opens and the zoospo- 

 rangia are emitted. Each zoospore, as it leaves the zoo- 

 porangium, is usually in active motion, being propelled by 

 the rapid lashing of two vibratile cilia which are attached 



1 De Bary and Woronin. " Uutersucbuugen iiber die Peronosporeen 

 und SaprolegnicD," 1881. 



- 'Botanisclie Uutersucliungen,' Heft iv, 1881, p. 109, 110. 



' T\ hence the name a-aiz^ioQ, sapros, rotten, and Xtyvov, legnon., the edging 

 of a garment. 



