110 GEORGE LEFEVRE AND WINTERTON C. CURTIS 
investigators for we seem to have evidence that some fish are 
much less susceptible than others and that with such fish any con- 
siderable infection is an impossibility, the most striking instances 
of this being the German carp, minnows and darters. 
In the case of the carp, we have a fish admirably suited for 
carrying the hooked glochidia of Andonta and Symphynoia, but 
we have never been able to secure a successful infection of the gills 
of the carp with the hookless glochidia of the genus Lampsilis. 
The disappearance of the hooked glochidia Anodonta and Sym- 
phynota from the gills of the carp, as previously mentioned,is 
explicable upon the grounds given in our consideration of the rea- 
sons for the survival of the two types of glochidia upon the fins 
and gills respectively but any such explanation is impossible 
when applied to this disappearance from both gills and fins of the 
glochidia of Lampsilis. 
With minnows (Notropis cayuga and N. lutreusis) two to four 
inches in length, we have not been able to secure any considerable 
infection with the glochidia in Symphynota complanata, for, 
though they will attach in large numbers during infection, they 
all drop from the fins and gills within a few days. The fin of 
these minnow^s, is much more delicate than that of the carp and 
the explanation is perhaps that so large a glochidium is easily 
torn away; but the large mouthed black bass has hardly a deli- 
cate fin, and for it we have records of infection where no glochi- 
dia of S. complanata attached during an exposure sufficient for 
the attachment of many to the gills. In this case, the extreme 
activity of the fish must be considered as a factor which might 
keep the hooked glochidia from attachnient to the fins. 
With darters, (Etheostoma coeruteam spectabile) one and one 
half to two inches in length, there appears to be an almost com- 
plete immunity against the permanent attachment of Lampsilis 
glochidia, for though they may fasten so thickly to the fins 
that many fish are killed within the first day after the exposure, 
the fish which survive this will slough off considerable portions of 
the fins and within a week show only the healed and regenerating 
parts as an indication of their recent experience. Such cases as 
these are of great importance and should be followed up to deter- 
