60 The Fungus of Salmon Disease. 



from the zoospores, with their rapid growth and ready germi- 

 nation in quickly succeeding generations. Such favourable 

 conditions to their life are not attendant in our climate.* 



With favourable conditions, the ordinary life history of the 

 fungus of salmon disease is very constant. The spore, after 

 taking root and sending out its branches in search of food, 

 sends off the ordinary stems or hyphae from them. These 

 appear at first as a quantity of protruding stems, rounded at the 

 ends, and in very close proximity to one another. They grow 

 out into the liquid straight from the roots, and their filaments 

 appear at times like a bunch of carrots, but instead of being 

 pointed they are of a fairly regular diameter for their full 

 length. The length to which these filaments grow varies 

 greatly ; they may on a fish be an inch or more in length, but 

 in cultivation often do not become longer than -| in. When 

 young and developing, these stems are beautifully clear, and 

 appear like long tubes, with no marking or division, but as de- 

 velopment proceeds they become darker, owing to the accumu- 

 lation of protoplasm. In time they gradually swell at the ends, 

 and become round or pear-shaped, or sometimes club-shaped, 

 after which they darken more and more, and at the base of the 

 enlargement a division appears, which prevents the further 

 circulation of the protoplasm. This club-shaped enlargement 

 is called a sporangium, and the zoospores are matured within it 

 by a gradual process which is very interesting to watch. The 

 dark mass of protoplasm in the sporange soon appears to be 

 divided into a number of small sections which, gradually be- 

 coming lighter or more transparent at their edges, are seen soon 

 afterwards to be round, and present the appearance of a mass of 

 well-developed seeds, lying closely packed together like shot in 

 a cartridge. This process of maturing may last twenty minutes 

 or half an hour, and when complete the apex or end of the club 

 is generally seen to have a pointed or beak-like shape. When 



* Since writing the above I have had such a favourable series of oospore cultivations 

 as to cause me to considerably change those views. {See Note, p. 62.) 



