322 SPENCER WALPOLE AND T. H, HUXLEY. 



of the S. ferax group. Up to the last-mentioned date, 

 however, no oosporangia appeared on any of these cultures. 

 The course of events was this : for two or three days 

 zoosporangia were very abundant, and thousands of zoo- 

 spores were set free. But, in no case which came under 

 observation, for several months, Avere these zoospores pro- 

 vided with cilia, or actively locomotive. They were dis- 

 charged from the zoosporangia as simple spherical corpuscles, 

 which flowed passively away, and were very often seen 

 germinating by sending out a single delicate hypha. 

 Immense numbers of these spores accumulated among the 

 hyphse.^ 



After this condition had lasted for a day or two, the ordi- 

 nary zoosporangia diminished in number, and " dictyo- 

 sporangia" made their appearance in place of them. In other 

 words, the spores, instead of being discharged, were retained 

 within the zoosporangium, and began to germinate in that 

 position. 



At the same time the protoplasm accumulated in certain 

 regions of the hyphse, which often became swollen, and these 

 accumulations were shut off from the rest by transverse par- 

 titions. The hyphse thus assumed a jointed or beaded 

 appearance, as in the S. torulosa of De Bary, and the joints 

 might eventually separate from the intervening empty parts 

 of the hyphse as a sort of buds or gemmce, which, after de- 

 tachment, might begin to germinate by throwing out delicate 

 hyphse at one or many points. Sometimes these buds were 

 terminal and spheroidal and closely simulated oosporangia, 

 but they did not give rise to oospores. No trace of antheridial 

 branchlets was ever visible. 



In the third week of April, however, oosporangia and 

 antheridia, in all respects similar to those of the " monoica'^ 

 form oi Saprolegyiia ferax, made their appearance in a copious 

 growth of the fungus on a fly, Avhich was infected on the 



^ Among previous observers, Mr. Stirling and Mr. W. G. Smith describe 

 and figure locomotive zoospores as if tbey were of ordinary occurrence. 

 Mr. Brook, on the other band (" Notes on the Salmon Disease in the Esk 

 and Eden," 'Transactions of the Botanical Society of Edinburgh,' 1879), 

 appears never to have seen locomotive zoospores : and Mr. George Murray, 

 of the Botanical Department of the British Museum, who lias been kind 

 enough to make a series of observations and experiments, continued over 

 six or seven weeks, on crops of Saprolegnia, raised upon dead flies infected 

 from Conway salmon, has met with the same negative results. Quite 

 recently, however (March 16), locomotive zoospores have been emitted 

 from one of our specimens of salmon fungus cultivated on bladder. But, 

 as in our specimens, so in those cultivated by Mr. Murray, no trace of 

 oosporangia had appeared up to that time. 



