NATURAL HOSTS OF FRESH-WATER MUSSELS. 
109 
Mucket {Lampsilis ligamentina) . 
On the 26th of September a rather large Roccus chrysops was taken holding upward 
of 200 glochidia of this species; cysts are heavy but glochidia show no development at all, 
so that it is presumed to be a recent infection. 
A great many other fish were taken during September and October, principally 
crappie and sunfish, infected with this mussel, but as the crew of the station were at 
work infecting and liberating fish with this larva, all were presumed to be artificial 
infections. No Roccus had been artificially infected previous to September 26, so that 
the above record is deemed permissible. 
Black Sand-shell {Lampsilis recta). 
The only time this mussel has been found a natural parasite was July 2, 1912, when 
a Lepomis pallidus was taken bearing 35 glochidia. The infection was recent, deeply 
encysted, and I have no doubt would have metamorphosed in a very short time, the 
fish being extremely strong and robust. 
Deer-toe {Plagiola donadjormis) . 
This small mussel, so far, seems to be found almost exclusively on the sheepshead, 
the only exception being a sauger taken quite recently. Discovered first at New Boston, 
111 ., in August, 1910, it has since been found at frequent intervals, both there and at 
Fairport. 
The number of young mussels found on a fish varies considerably, but is usually 
great, a fish taken October 30 holding about 2,800, which is the greatest number found. 
The duration of parasitism is problematical; no fish have been found recently infected, 
all infections so far found being highly developed. As we have secured gravid mussels 
of this species with fully developed glochidia only during the latter part of July, it 
seems probable, and is possible, that the enormous development indicated occurs in the 
short space of two months, but this of course can only be proved by artificial infection 
of the specific host. Specimens of least development, so far known, are some taken 
July 20, 191 1 , one of which is shown in figure 8 (postero-dorsal view) ; this would indicate 
one of two facts, either that it was an infection of the previous year, in which case 
growth is comparatively slow, or that it was very recent and growth correspondingly 
rapid. On a fish taken August 16 occur 1,495 young mussels, the development of 
which is very great, far exceeding that shown previously in Icevissima; one in side 
view is shown by figure 9, which is found to have increased seven times in length, 
and about three and one-half times in depth over glochidial shell, yet all on this fish 
were not uniformly developed, as is shown in figure 10 (o). Figure 10 shows a portion 
of a filament with young mussels in situ, two of which are on the edge, while the other 
(a) is encysted on the flat side of the filament. 
60289° — Bull. 32 — 14 8 
