344 Miscellaneous. 



sent the ultimate limit of the evolution of the parasite, we have 

 met with a whole series of younger stages, which has enabled us to 

 follow the development of the spores, and thus to fill up the gap 

 which existed in the history of the parasite of Palcemon. 



Here, in fact, by the side of ripe spores we have observed little 

 spheres of plasma, provided with a nucleus. These little elements 

 are surrounded by a delicate envelope of a hyaline substance which 

 resists the action of potash. They measure about 12 ^ to 14 ^ in 

 diameter. 



We soon observe that the nucleus loses its membrane and assumes 

 the arrangement known as the chromatin wreath (" peloton chro- 

 matique"). We next witness the formation of an equatorial plate, 

 then its division into two, and so on. 



It is therefore seen that we are dealing with a case of fission by 

 liaryokiuesis. We did not succeed in obtaining a clear view of the 

 achromatin fibres, probably in consequence of the small dimensions 

 of the elements. The indirect division of the nucleus in the Myxo- 

 sporidia has, moreover, already been described by one of us *. 



After the division of the nucleus the plasma soon divides in its 

 turn, and we observe within the envelope two little nucleated 

 masses. The same phenomena of fission are repeated, and by 

 means of successive bipartitions we finally get within the envelope 

 eight little nucleated masses, at the expense of each of which a spore 

 will be formed. It is impossible to follow the formation of the 

 latter in detail in consequence of its small dimensions. 



To recapitulate our results. The organism which we have 

 observed in Crangon must be assigned to the Myxosporidia, since 

 its spores enclose an eversible filament. 



It is interesting on account of its habitat, for Myxosporidia had 

 not hitherto been stated to occur in Arthropods, except in Tortrix 

 viridana by Prof. Balbiani. 



This parasite is very closely allied to Gltigca and to the parasites 

 of Cottus and Callioni/mus ; it differs from them by the constant 

 number (eight) of sjiores which develop in each ripe vesicle. 



It has enabled u.s to confirm the observations made by one of us 

 with regard to karyokinesis in the Myxosporidia. 



Lastly, it is so intimatelj' related to the parasite of Falremon that 

 we may, we believe, extend to the latter the results of our observa- 

 tions. — Conrptes Rendus hebdomadal res des seances de la Societe de 

 Biologic (Seance du 25 juin, 1892) : from a separate impression, 

 communicated by the Authors. 



* Thelohan, " Recherches sur le developpement des spores chez les 

 Myxosporidies," Comptes Ilendus de I'Academie des Sciences, November 

 1890 (Ann. & Mag. Nat. Hist., March 1891, pp. 304-306). 



