210 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



Thelobau ^ was the first to recoj?nize their nuclear nature. He first 

 believed them to beloug to the sporoplasin, supposing them to be situ- 

 ated at its 2 antero-external angles (lateral cornua). Subsequently, 

 from a study of capsule development, he^ regarded the bodies iu ques- 

 tion as persistent embryonal uuclei, the remnants of such develoj)ment. 

 He further expressed the belief that these nuclei could in some cases 

 become detached from the capsules and engulfed in the sporoplasm. 



Pfeifter- terms them '' safranophile corpuscles," but does not comment 

 upon their nature. In Myxobohis macrurtis I have studied these bodies 

 (which, from their position, may be termed pericornual nuclei) with 

 great care, and with the following results, which apply especially to 

 M. macrurtis, but equally well to M. Untoni: 



1. There can be no question whatever that they are nuclei, as they 

 take nuclear stains and show nuclear structure. 



2. Their presence or absence and their position (at least in the fully 

 developed siwre) appears constant for the Same species; As regards 

 constancy of position they contrast strongly with the third and fourth 

 nuclei. 



3. The only question is as to their seat. It will be seen above that 

 they have been regarded as belonging to the capsule and also as 

 belonging to the sporoplasm. As is implied by this difference of ojtinion, 

 their seat is by no means easy of determination, and, after much study, 

 I am as yet uncertain whether they are capsular or sporoplasmic. 



Three appearances may sometimes be seen on the same specimen : 

 {a) They appear in one focus-plane almost certainly connected with the 

 infero-lateral cornu; or, (b) they appear almost as certainly attached 

 to the drawn-out posterior end of the capsule; or, (c) they appear discon- 

 nected from both and appear to be borne on a broad triangular spur 

 projecting inwards from the shell. 



An interpretation which seems possible is that each nucleus is 

 imbedded in the sporoplasm near the tip of the siy;ero-lateral cornu, 

 whence it happens that optically its position almost exactly coincides 

 with that of the posterior end of the capsule. 



In some species {Myxohohis cf. linearis, M. transovalis) I failed to 

 find any bodies which on account of the constancy of their i)osition, 

 etc., I could regard as the pericornual nuclei, and this absence appears 

 to be here as definite a specific character as does their x>i'eseuce in ill. 

 maerurus and M. Untoni. 



34. Myxobolus unicapsulatus Gurley, 1893. PL 13, lig. 1. 



(Psorosperm of Laheo niloticus Miiller, 1841, Miillcrs Arcliiv., p. 487, pi. 16, fig. 

 5 a-d; ib. Robiu, 1853, Hist. Nat. d. V6g6t. Parasites, p. 299, pi. 14, fig. 7.) 

 Mijxoholus imicapsulatus, Bull. U. S. Fish Com. for 1891, xi, p. 414; ih. of Lahro 

 [error] niloticus Braiiu, 1894, Centralbl. f. Bakt.ii. Parasitenkde, xv, p. 86. 

 Cyst and myxosporidium unknown. 



1 Compt. Rend. Acad. Sci. Paris, 1889, cix, pp. 920-1 ; ibid., 1892, cxv, p. 1097. 

 ^Die Protuzoen als Krauklieitserreger, 1891, 2 ed., p. 7. 



