THE SPOROZOA 



291 



ever, that before the parasite arrives at its destination, it goes 

 through developmental processes of which it is only possible as 

 yet to form a conjecture. Doflein has drawn attention to the 

 noteworthy fact that while the sporozoite of the Phaenocystes always 

 contains two nuclei, the youngest observed trophic stages have but 

 a single nucleus, and he has suggested that this difference is due 

 possibly to conjugation, leading to an exchange and subsequent 

 fusion of nuclei, taking place between the free amoebulae. No con- 

 jugation has been observed as yet in any stage of the life-history, and 

 this fact makes it the more probable that some form of conjuga- 

 tion takes place at a very early stage, having in view further the 

 great reproductive powers which these parasites exhibit even in the 

 youngest stages of development. Conjugation at this early stage 

 would find a parallel in the frequently occur- 

 ring conjugation between swarm spores in 

 many Ehizopods. 1 



Like many other Sporozoa, the Myxo- 

 sporidia possess the power of endogenous 

 reproduction within the host, as well as of 

 exogenous reproduction by means of spores. 

 Doflein has aptly distinguished these two 

 modes of reproduction as the multiplicative 

 and the propagative methods respectively. The 

 former is comparable in a general way to the 

 schizogony of Telosporidia, though differing 

 in details. It has long been suspected to 

 occur in the Myxosporidia on account of the 

 vast number of parasites that may be present Myxiatum lieoerlculinn> BUt 

 in a given host, and the difficulty of supposing schii (par. ESOX and Lota\ 



,1 , i ., 111 r j at 'ter Cohn. b buds ; end, 



that each parasite could have originated in endopiasm ; the clear outer 

 eaxjh case from a separate and independent gjjjj; 1 re P resents the ect0 ' 

 spore infection. It is only in recent years, 

 however, that it has been demonstrated by Cohn [99] and Doflein 

 [100] in various forms. Multiplicative reproduction may take 

 place in one of two ways. In the first place, it may go on in the 

 full-grown trophozoite, either by simple binary fission, similar in 

 externals to that of an ordinary amoeba, or by the formation of 

 buds from the protoplasmic body. 2 Doflein has termed this process 



1 According to Stempell [111, p. 262, footnote], Schaudinnhas observed "copula- 

 tion of the amoeboid germs of a spore " (sic) in Olugea bovibycis. The publication of 

 these observations will be awaited with interest. Stempell considers that the four 

 nuclei seen by him in spores previous to germination (p. 285 supra, Fig. 92, m) re- 

 present a process of nuclear reduction preliminary to the conjugation. 



2 Laveran and Mesnil [106], however, deny that the budding described by 

 Cohii occurs. They find that in Myxidium lieberkiihnii endogenous multiplication 

 goes on by equal or subequal plasmotomy in young trophozoites, and that these 

 small forms often attach themselves to the surface of the body of large individuals, 



FIG. 101. 

 Formation of buds by 



