5132 Fishes. 



Mucedo, and it appears to me to be both an indication of extreme vital 

 energy in the reproductive process, and also an arrangement, the ob- 

 ject of which is evident, to enable the spores in their development to 

 spread more rapidly over a more extended surface, and to interfere less 

 with each other in their mutual growth. Having thus obtained a second 

 condition of this plant, in which it is a rapidly budding unicellular 

 body, I watched with much care for its return to the tubular form, and 

 was able to trace it pretty perfectly. As the masses of cells developed 

 they became rather larger in bulk and less defined (their utricle or 

 limiting membrane, if at all existing, being of extreme fineness), and 

 from the surface of the growth one of the cells developed the new 

 shoot, which resembled in all things the parent plant. 



It remains now to describe what I believe is new, at least as far as 

 my researches go, the fact that this unicellular rapidly-developing 

 condition of the plant is perfectly capable of destroying life in fish ; 

 many, indeed almost all of them which have recently died with me, and 

 I have now lost all my fish but three, have presented this state of plant 

 alone (at least during life). It adheres in dense masses to the fins, the 

 tail, and even to the edges of the scales over the body ; it collects on 

 the gills, disorganises them, breaks down the higher organised tissues, 

 lays bare the cartilaginous structures in the gills, tail and fins, and 

 interfering with respiration (as it seems to me), proves even thus more 

 rapidly fatal than from its more slow but equally certain destructive 

 action on the vital tissues. It is impossible not to recognise in this, 

 which might be termed a " mycelium stage," a strong analogy with the 

 mycelic stage of Fungi. We know how dry rot, for instance, produces 

 its destructive ravages in wood in its rapidly growing mycelial condi- 

 tion, not in its more advanced state of development, and I have, in my 

 researches on this subject, become strongly impressed with the con- 

 viction that it is to this as yet unrecognised state of the Saprolegnia 

 we are in reality to ascribe much, if not all, of the destructive action 

 which it exerts on animal life. In fact, I believe we have in it a clear 

 instance of a plant causing disease in healthy bodies, and not, as is too 

 commonly believed, a mere vegetative growth developed on a body 

 already in a state of ill health. Such is, indeed, the general doctrine 

 held with reference to epiphytic growths occurring in disease, which 

 are frequently regarded as accidental epiphcenomena, whereas their 

 invariable presence alone in such cases would of itself go far, to the 

 unprejudiced mind, to prove a more intimate connection between 

 them and the diseased condition which they accompany, or, as I think, 

 frequently produce. 



