THE SPOROZOA 



285 



which are frequent, the chief developmental variations are seen in the 

 number of polar capsules, of which there may be only one, or as many as 

 four. The latter number characterises the Chloromyxidae, and in this 

 family twelve or fourteen nuclei are found in the pansporoblast, and five 

 or six in each definitive sporoblast (Doflein [100]). 



In the Cryptocystes the pansporoblast always gives rise to more than two 

 spores, namely, to four in Gurleya, eight in Thelohania, and to a large number 

 in Pleistophora and Glugea. Further peculiarities 

 are seen in the origin of the pansporoblast in this 

 sub-order. In Glugea, numerous pansporoblasts 

 are formed in each trophozoite, just as in the 

 polysporous Phaenocystes, but in Gurleya, Thelo- 

 hania, and Pleistophora, the whole trophozoite 

 becomes converted into a single pansporoblast, thus 

 producing a state of things which only differs from 

 Coccidium or any other Telosporidian type in the 

 fact that the spores are formed endogenously, in 

 the bosom of the protoplasm, and not at its outer 

 surface. An approach to this condition is also 

 seen in the disporous Phaenocystes, where only one 

 pansporoblast is formed in each trophozoite, the 

 remaining protoplasm, with the contained nuclei, 

 being left over as residual protoplasm which dies 

 off ultimately (Fig. 91). It would not be safe, 

 perhaps, to regard these forms which produce a 

 single pansporoblast as connecting links in any 

 way between the Telosporidia and the Neospo- Ceratomyxa inaequaiis, 



. ,* , ,, . r Dofl. (par. Crenilabrus), tro- 



ridia, but they are certainly suggestive in con- phozoite containing two 

 sidering the relationship between these two sections u S?y es n uSei an (r n) W other 

 of the Sporozoa. The Myxosporidia might be letters as before. (After 

 regarded as forms in which the trophozoite pro- em 

 duces typically a greater or less number of sporonts (i.e. pansporoblasts) 

 by a process of internal gemmation. On this view, the typical life-cycle 

 of the Myxosporidia would represent an alternation of generations between 

 trophic and reproductive individuals. 1 



The development of the pansporoblast or sporont of Thelohania mulleri 

 has been followed in detail by Stempell [111]. The nucleus divides 

 without mitosis into eight nuclei, round which the protoplasm becomes 

 segmented to form eight sporoblasts, imbedded in an intercellular residuum 

 within the envelope of the sporont (Fig. 92, a-i). Each sporoblast becomes 

 a spore, which has first one nucleus, later two (Fig. 92,^-Q. Stempell 

 has made the further remarkable discovery, that when a fresh host 

 (Gammarus) is artificially infected, the spores remain some time in the 

 gut before germinating, during which period the two nuclei divide, so 

 that the spore ready to hatch has four nuclei (Fig. 92, m). 



1 Since this paragraph was written (in 1901), Qtempell [111, p. 265] has dis- 

 cussed the relation between "sporont" and "pansporoblast," and has suggested 

 that the sporonts of Thelohania and similar forms are " pansporoblasts which in the 

 course of the phylogenetic development have become independent individuals." 



Fio. 91. 



