198 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
Life history.—All the individuals, whether wholly or only partly 
invaded, showed the same developmental stage. It seems fair to sup- 
pose the first stage to be a plasmodioid mass in which the spores form. 
The constant presence of 8 spores suggests their origin by successive 
bipartition, as occurs with the falciform corpuscles of Gregarines (Hen- 
neguy, 1888). The stage of development of the parasite of P. serratus, 
taken in connection with the date of capture, indicates that the course 
of development of the parasite is the same in this crustacean as in P, 
rectirostris (Henneguy and Thélohan, 1892). 
OCyst—Henneeguy vainly endeavored to detect, even under very high 
powers and with different reagents, in material, fresh or fixed, disso- 
ciated or sectioned, a cyst membrane, and believes the cyst to be 
absent. This view is, he thinks, confirmed by the irregularity of the 
distribution of the pansporoblasts between the fibrille. 
Pansporoblast (“ vesicles” of Henneguy, 1888).—Rounded, diameter, 
10 «; membrane thin, transparent, resisting potassium hydrate solution, 
apparently not presenting local thickenings as in 7. giardi. 
Spore formation.—Each pansporoblast produces 8 spores, which fill 
only a portion of its cavity and are disposed without order. 
Spore.—Length, 3 to 4 4; pyriform, very refringent; capsule present; 
length of filament 40 to 50 4; exit, produced, after failure of all other 
reagents, by ether, whose action is rapid and perfectly definite, and 
affects a large number of spores; usually extruded completely, some- 
times, however, only partially uncoiled ; capable of staining with anilin 
stains, among others violet 5B, The electivity of the filament for ether 
is a striking peculiarity. 
Habitat.—Interior of muscular fibers (between the ultimate fibrillz) 
of Palemon rectirostris Zadd (prawn), from the sait marshes at Le Croi- 
sic; the same seat in P. serratus from Conearneau and from Roscoff. In 
P. serratus less common than in P. rectirostris, in which latter it is (at 
least at Le Croisic) extremely frequent. It is never found in the diges- 
tive tract, nervous system, glands, sexual organs, or anywhere but in 
the muscles. 
Affinities.—By its exclusive seat in the muscles, and by the form and 
grouping of the spores, the parasite appears to be incontestably a sar- 
eosporidian, differing from those of the Mammalia in the absence of a 
surrounding membrane... The spores, also, are a little different from 
those of the other Sarcosporidia. They recall certain myxosporidian 
spores. This form also presents much affinity with the Microsporidia 
of the Arthropoda, the latter having the same refringent aspect and 
more or less oval shape of the present species, and being, like it, inclosed 
in “vesicles.” One finds them in all tissues, but not in the interior of 
the muscle fiber. There, then, probably exists a rather close relation 
between the Micro-, Myxo-, and Sarcosporidia, and the parasite of 
Palemon appears to represent a transition form between the 3 groups 
(Henneguy, 1888). 
