210 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



Th^lohau ^ was the first to recoffuize tlicir nuclear nature, lie first 

 believed them to belong to the sporoplasm, supposing theiu to be situ- 

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

 from a stud^^ of capsule development, he' regarded the bodies in ques- 

 tion as persistent embryonal nuclei, the remnants of such development, 

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

 become detached fi-omthe capsules and engulfed in the sporoplasm. 



Pfeift'er"^ terms them "safi-anophile corpuscles," but does not comment 

 ui^on their nature. In Mi/xobolus maeruriiH 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. macrurus, but equally well to J)/. Untoni: 



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

 take nuclear stains and sh.ow nuclear stru(;ture. 



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

 develoi)ed spore) appears constant for the same species. As regards 

 constancy of j)osition they contrast strongly with the third and fourth 

 nuclei. 



3. The only qnestion 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 opinion, 

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

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



Three appearances may sometimes be seen on the same specimen : 

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

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

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

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

 projecting inwards from the shell. 



An interpretation which seems possible is that each nucleus is 

 imbedded in the sporoplasm near the tip of the super o-hxt^dT'dX cornu, 

 whence it happens that optically its i)osition almost exactly coincides 

 with that of the jjosterior end of the capsule. 



In some species {Myxoholus cf. linearis, M. transovaUs) I failed to 

 find any bodies which on account of the constancy of their position, 

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

 to be here as definite a specific character as does their x)resence in M. 

 macrurus and M. Untoni. 



34. Mysobolus unicapsulatus Gurley, 1893. PI. 13, lig. 1. 



(I'soiosiiorm of Laheo niloticus Miillor, 1841, Miiller's Arcliiv., p. 487, pi. 16, fig. 

 5 a-d; ib. Robiu, 1853, Hist. Nat. d. Vogdt. Piirasites, p. 299, pi. 11, fig. 7.) 

 Mijxobolua unicapsulatus, Bull. U. S. Fish Com. for 1891, xi, p. 414; i6. of Lahro 

 [error] niloticus Hrauii, 1894, Ceutralbl. f. Bakt. u. rarasitenkdo, xv, p. 8G. 

 Cyst and myxosporidium unknown. 



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

 'Die Protozoeu ala Krauklieitscrreger, 1891, 2 ed., p. 7. 



