900 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
that each space corresponds to a primitive fiber bundle whose normal 
aspect is profoundly modified by the presence between its fibrille of 
elements of a parasitic nature, whence results a slight increase of width 
of the fiber bundle. Most often the fibrille do not present a sensible 
alteration. Sometimes (probably when a great quantity of the para- 
sitie element has led to a considerable separation) the elasticity of the 
fibrillxe is overcome, rupture resulting. Even under these conditions, 
however, the muscle strive remain exceedingly clear, no degeneration 
ever having been observed, as in Callionymus and the barbel. 
The nuclei of the muscle fiber are more numerous and smaller than 
normal; this feature is particularly well shown by safranin (Henneguy, 
1888). 
Effects —The muscular vigor is considerably diminished. Thus, if a 
number of P. rectirostris living in the rivulets of the salt marshes be 
frightened out of their shelter among the vegetation, even although 
the new shelter sought by them be near at hand, the diseased white 
individuals (immediately recognizable against the strongly contrasted 
muddy rivulet bottom) lose grourd and remain considerably behind the 
sound ones. Further, one knows with what ease the prawns jump out 
of the vase in which they are held captive. If sound and opaque 
prawns be placed together in a basin, after some hours the sound ones 
have nearly all dispersed around the vessel, while the opaque are there 
still, or have only succeeded in sticking to the wall of the basin, how- 
ever small the bound required to overleap the barrier. Considering 
the intensity and universality of the muscle infection, the diminution 
of muscular vigor is quite natural; indeed, the surprising feature is 
the relatively great agility retained by muscles the bulk of whose con- 
tractile substance is much inferior to that of the parasite, and in some 
cases it is truly astonishing that muscular power is not completely 
destroyed. Among the diseased Palemons no egg-bearing females 
were seen. Perhaps this may be a case of “ parasitic castration.” The 
diseased individuals do not survive very long, all succumbing by the 
end of autumn, as during the winter not one can be found. 
Conditions and mode of infection The prawns affected are usually 
found in small shallow ditches containing a layer of water 0:10 m. to 
0:20 m. deep, along the slope separating the compartments from the 
salt marshes. The water of these ditches is rarely renewed and acquires 
an elevated temperature. These are probably the conditions favorable 
to the development of the parasite. Itis difficult to decide whether 
the parasite finds an entrance by way of the alimentary canal. Hen- 
neguy seems to favor the contrary view, as the first lesions are found 
at places remote from the digestive tract. 
Artificial infection.—Captive Palemons fed for several months with 
diseased tissue showed no signs of infection. It was impossible to pro- 
long the experiment to see whether infection would ultimately ensue 
(Henneguy, 1888). P. rectirostris fed for months with diseased tissue 
