104 GEORGE LEFEVRE AND WINTERTON C. CURTIS 
reach the gills by way of the mouth and not from the opposite 
direction. For fin infections, sluggish fish like the German carp 
need Uttle attention, and the darters (Etheostoma cceruleumspec- 
tabile) which habitually rest upon the bottom for considerable 
periods, become quickly loaded with glochidia upon both fins and 
gills, though as we shall see, the latter appear to be particularly 
adapted for ridding themselves of the entire infection. 
Infections with hooked glochidia 
For the infections with hooked glochidia, we have used prin- 
cipally Anodonta cataracta from Falmouth, Massachusetts, the 
species studied by Lillie ('95). With these, we have, infected 
German carp under six inches in length and, unless otherwise 
stated, the following account refers to this combination which 
gives typical results. A smaller number of infections made with 
Symphynota complanata and S. cost at a upon carp and other fish 
are referred to in a supplementary manner. The glochidia of A. 
cataracta become attached in large numbers to the fins (Figs. 7-11 
and gills of the carp. They are also found upon the other external 
parts which offer the condition of a soft scaleless epithelium like 
that of the fins; thus the region about the anus, the edge of the 
operculum, the lips and, in very heavy infections, even the soft 
area of the ventral surface between the mouth and pectoral fins 
may become heavily loaded. Within the mouth cavity, the gill- 
filaments and also the gill-bars and rakers become well covered. 
The glochidia which attach to these mouth parts do not remain, 
for, though the fish may be carrying many of their fellows upon its 
external parts, in about one week after the infection all glochidia 
have disappeared from the gill-filaments, which then become 
as clean as though never infected. There is some chance of a 
scattering of glochidia remaining upon the other internal mouth 
parts, for such specimens are occasionally seen well embedded and 
in advanced stages of their metamorphosis, but in the main, these 
parts also will become free of glochidia. 
The general distribution upon the individual fins may be seen 
by reference to figs. 7-11, which show how great a proportion 
