LIFE-CYCLE OF " CYSTOBTA " IRREGULAEIS (mINCIl). 59 



even tliongb association should prove to be lateral also in 

 C. liolothurifB. 



With regard to the variation in the shape and position of 

 the sporozoite-nucleus shown in the different cases it is a 

 little difficult to know what value^ if any, to assign to these 

 differences, since it is somewhat uncertain whether the sporo- 

 zoites, as thus compared, are equally ripe. Minchin (25) 

 considers the sporozoites of C. holothuri?e, in the form of 

 the definition, as not, perhaps, quite mature, and appears to 

 think that their nucleus may ultimately become elong-ated. 

 If that is so, the same may also be true of C. minchinii. 

 Possibly, moreover, the sporozoite-nucleus in this species 

 subsequently takes up a position near one end, but in any 

 case the point is, at most, one of minor specific importance. ^ 



It is otherwise with the difference in the form of the 

 spore exhibited by C. holothurite, which is not sufficiently 

 emphasised by its present position, especially when we bear 

 in mind the importance attached to this character in dis- 

 tinguishing the different coelomic Gregarines. C. holothurire 

 has been hitherto united with C. irregularis, largely on 

 account of the similar habitat and precocious association. 

 Both of these features, however, may have been independently 

 acquired by another parasite. We see the latter condition 

 strongly developed in quite a different Gregarine — namely 

 Diplocystis — and, granting that another form also become 

 parasitic in the peculiar situation of C. irregularis, it would 

 be most likely to develop the same intimacy of association. 

 Again, the distribution of C. irregularis and C. holo- 

 thuriae is, so far as is known, quite distinct. Hence, con- 

 sidering everything, it seems probable that these two species 

 ai'e not ver}^ closely related (one being derived from or throuo-h 

 the other, as, for instance, C. minchinii almost certainly is 



' The position of t'.ie sporozoite-nucleus is not invariably tlxed or constant 

 even in one and the same species. In the case of the sporozoites of 

 Urospora lagidis, Brasil (loc. cit.) finds that, while the nucleus is 

 usually more or less central, it may be near either one end or the other 

 (compare his figs. 79 and 80). 



