The Fungus of Salmon Disease. 61 



the spores are fully matured they press on the pointed end of 

 the sporange until it opens, when they hurriedly escape, one at 

 a time, into the liquid, and quickly settle down if there is no 

 current to carry them away. These zoospores, as previously 

 described, possess two hair-like tails, which by rapid movement 

 give them motion, but although they are usually credited with 

 lively movement immediately after liberation, this is not always 

 the case with the species I have had under observation. After 

 emission they become protected with a thicker coating or cell- 

 wall, and at a varying time afterwards are known to become 

 endowed with a second period of movement, which may last for 

 as long as twenty-four hours, the object of this evidently being 

 to assist them in searching for a suitable nidus to grow upon. 



After the zoospores are liberated the empty sporangium gra- 

 dually disappears, and its place is again filled by another 

 sporangium, which has been forming on the same stem during 

 the time the previous crop of zoospores were maturing. It 

 presses forward into the place of the old one, or inside it, and 

 there the process of spore formation again goes on, and con- 

 tinues at intervals of half an hour or so until the protoplasm 

 collected in the hypha is exhausted. The number of spores 

 that may thus be liberated by such a continuous process can 

 easily be seen to be enormous. 



The oosporangium and its contained oospores, as before men- 

 tioned, are generally formed at unfavourable periods, when the 

 ordinary spores above described cannot be produced. A bulg- 

 ing appearance then starts at any part of a healthy stem, and 

 pressing outwards as a ball-like protuberance, again thins down 

 to a slight stem at the point where it joins the original stalk. 

 In this round, ball-like cell several spores are formed called 

 oospores. These spores are not liberated, as in the case with 

 the zoospores, but may remain there protected for an indefinite 

 time, or may be liberated by the cell wall opening to allow them 

 to escape ; the continuation of unfavourable influences would 

 probably cause them to remain together until a chance for their 

 germination occurred. It is pointedly mentioned by Professor 



