198 REPORT OF THE COMMISSIONER OF FISH ANU FISHERIES. 



Life historij. — All tlie 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 Th^lohau, 1892). 



Cyst — Henneguy 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 pansx)oroblasts between the fibrillte. 



Pansporoblast (''vesicles" of Henneguy, 1888). — Bounded, diameter, 

 10 /i; membrane thin, transparent, resisting potassium hydrate solution, 

 apparently not presenting local thickenings as in T. giardi. 



Spore formation. — Bach pansporoblast produces 8 spores, which fill 

 only a portion of its cavity and are disposed without order. 



Spore. — Length, 3 to4 /^; pyriform, very refrin gent; capsule present; 

 length of filament 40 to 50 //; 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 oB. The electivity of the filament for ether 

 is a striking peculiarity. 



Habitat. — Interior of muscular fibers (between the ultimate fibrillae) 

 of Palcemon rectirostris Zadd (prawn), from the salt marshes at Le Croi- 

 sic; the same seat in P.serratus from Concarneau and from Eoscoff. 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- 

 cosporidian, 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 myxosporidiau 

 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, tlien, probably exists a rather close relation 

 between the Micro-, Myxo-, and Sarcosporidia, and the parasite of 

 Palcemon appears to represent a transition form between the 3 groui)S 

 (Henneguy, 1888). 



