80 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



In Thelohania the inyxosporicliuni appears to be absent (completely 

 tranvsformed into pansporoblasts?); the pansporoblast constantly dpo- 

 dnces 8 spores. 



The process in Cystodiscus is imperfectly known (see p. 280). 



Nothing is known of the process in Sphwromyxa. 



The rule in Myxoholus appears to be pansporoblastic spore formation 

 with tripartite sporobJast serimentation. Although at first sight M. miil- 

 leri appears to constitute an exception to the rule, I have endeavored 

 elsewhere (p. 218) to show that this species really conforms to it. 



(Jhloromyxum (as represented by C. leydigii-, also C.incisnm) through- 

 out all its various habitats is characterized by monosporogenetic pan- 

 sporoblastic spore formation. In C. mucronatum, however, Lieberkiibn 

 appears to have observed 2 sj)ores in the x^ansporoblast. 



Nothing is known of the process in Sphca'ospora. 



In Myxosoma also nothing is known beyond the fact that the spores 

 are developed within a myxosporidium. 



Beyond the very striking peculiarity of bisporogenesis, nothing is 

 known as to the process in Ceratomyxa (see p. 274). 



Myxidium {M. lieherkUhnii) appears to be characterized by pansporo- 

 blastic spore formation, icithout sporohlast segmentation. As, however, in 

 M. lieberMhnii the developed capsule is a structure plainly separate from, 

 and not continuous in substance with, the sporoplasm, its abstriction 

 from the latter must occur at some period of the development. As this 

 abstriction would differ from the Myxoholus segmentation mainly in the 

 time of its occurrence, the real amount of difference between the 2 pro- 

 cesses becomes problematical.^ 



From the following (which, unfortunately, I have been unable to 

 examine further) it seems to me probable that Leuckart recognized the 

 pansporoblast as early as 1847. In speaking of the spores, he says:"^ 



Their formatiou takes place in an endogenous manner in the interior of special 

 cells, as I have already sliown in another place (Gottingische Gelehrte Anzeiger, 1847, 

 p. 1032). 



Leydig's description^ is as follows: 



A clear pale-contoured vesicle is first difi'erentiated, in which a number 



iProf. Biitschli (Bronn's Thier-Reich, 1882, i, p. 600) takes, apparently with special 

 reference to this species, the view that the capsules seem to lie not near, but in. the 

 sporoplasm, which appears to cover them with a delicate prolongation. ' This view 

 is also, he remarks, to be expected from the de\elopmental history. This, however, 

 doubtless means only that the capsules ai'e surrounded on all sides by the sporoplasm, 

 not that they are continuous in substance therewith. 



^Archiv. f. physiol. Heilkde, 1852, xi, p. 435. 



^Muller's Archiv., 1851, p. 226. Leydig, it will be remembered, erroneously regarded 

 this structure as a vesicle (Tochterblase). His observations were made upon Chloro- 

 myxum leydigii and C. incisum. 



