348 CONFERVA ON THE SKIN OF THE GOLD-FISH. 



and about 40 1 00 th of an inch in diameter. In structure they 

 were homogeneous, apparently gelatinous, and covered with a 

 fine membrane. 



This parasite propagates by spores formed in its terminal 

 articulations, which are developed into spore-cases for that 

 purpose. Having observed terminal articulations in all stages 

 of development, I may state the changes they undergo to be 

 the following : 



1. A perfectly barren terminal articulation is elongated, 

 spear-shaped, transparent, without granules. 



2. A terminal articulation which is destined to become a 

 spore-case does not elongate so much, and is from the first, 

 or at least from an early period of its growth, full of granules, 

 which give it a grey colour. It is also elongated, fusiform, and 

 connected to the penultimate articulation by a narrow neck. 



3. It becomes more distinctly fusiform, retaining its other 

 characters. 



4 The granules appear here and there to increase in size, 

 or at least larger granules appear diffused through the mass. 

 These larger granules or vesicles are more or less transparent. 

 The articulation now becomes cylindrical, with rounded ex- 

 tremities and a constricted neck. 



5. The articulation increasing in dimensions, but retaining 

 the same shape, contains a packed mass of perfectly trans- 

 parent globules, which are uncompressed and without appre- 

 ciable internal structure. 



6. The fertile articulation or spore-case bursts ; that is, I 

 have seen it with its contents hanging together from a rup- 

 ture in its walls. 



Proceeding to observe the changes which the spore itself 

 undergoes, I detected lying here and there, among the attached 

 extremities of the primary filaments, groups of spores corre- 

 sponding in numbers and characters to those which I had 

 seen escaping from the spore-cases. 



