346 CONFERVA ON THE SKIN OF THE GOLD-FISH. 



filaments, although individually transparent, were so close to 

 one another and so numerous that the mass appeared opaque. 

 When the lateral portions of the mass were separated along 

 the median line, so as to display the free edges of the fins, 

 these edges were observed to be shrivelled, not, as appeared 

 to me, by a process of ulceration, but by an irregular inter- 

 stitial absorption. This absorption was more evident along 

 the bounding edge of the parasitic mass, where it presented 

 the appearance of a furrow, in which 4he parasite grew with 

 more luxuriance than elsewhere. 



What was the exact state of the surface to which the 

 parasite adhered I am not prepared to say. I could detect no 

 substance corresponding to the false membrane described by 

 certain observers as constituting the soil on which vegetate 

 those parasites which infest the air-cells of birds ; neither 

 could I satisfy myself that the substance which formed the 

 infested surface was merely the mucous covering of the fish. 

 I am inclined, however, to lean to the latter opinion, for two 

 reasons first, because the surface exhibited the pigment cells 

 of the skin ; and secondly, because I detected solitary indivi- 

 duals attached to the broad scales of the back. 



Each plant consists of a jointed filament, in some indivi- 

 duals single, in others dividing dichotomously towards the 

 attached extremity, but more frequently near the summit. 

 The filament tapers gradually from the base to the summit. 

 The former is very slightly dilated, rounded and closed at the 

 extremity, which is destitute of appendages. The latter varies 

 in different individuals under different circumstances, as will 

 be afterwards described. The articulations are elongated, 

 varying in length from ten to fifty times their breadth. Basal 

 articulations were met with, having a breadth of the 800th of 

 an inch ; acute or barren terminal articulations were about the 

 2000th of an inch. The length of the articulations increased 

 towards the summit, the basal being in general the snortest. 



