156 THE PROTOZOA 



normal vegetative functions. It is a case of cellular division of labor 

 in which possibly some of the multiple nuclei are specially differ- 

 entiated for reproduction. The number of archispores formed in the 

 pan-sporoblasts varies in the different species and genera. In some 

 cases there is but one (Ckloromyxum), in others a large number 

 (filugea). The polar capsules, which are particularly characteristic of 

 this type of Sporozoa, also vary in number and in position. They 

 may both be at one end of the spore (anterior), as in Myxobolus (Fig. 

 83, K), at the two ends, as in Myxidium, or in the centre, as in 

 Ceratomyxa (Fig. 83, G). 



The Sarcosporidiida resemble the Myxosporidiida in forming spores 

 throughout life. The peculiar pouch, which corresponds to the amoe- 

 boid body of the Myxosporidiida and which may grow to a consider- 

 able length (up to 16 mm. in sheep), is filled with masses of nucleated 

 protoplasm which may be called pan-sporoblasts. Those in the 

 centre of the pouch become coated by a membrane and divide into a 

 number of germs or sporozoites known as Raineys Corpuscles, which 

 in some cases appear to have polar thread-bearing capsules similar to 

 those of the Myxosporidiida. The life-history and mode of infection 

 of new hosts is unknown. 



Conjugation is a well-authenticated phenomenon in at least three 

 orders : Hsemosporidiida, Gregarinida, and Coccidiida, although the 

 observations have not been numerous enough to warrant further 

 generalizations. Among the Haemosporidiida, where the intra-cellular 

 parasites frequently leave their cell-hosts, there is a shorter or longer 

 period of free life. During this period two individuals, upon meeting, 

 fuse together, forming one individual (Labbe). The nuclei also 

 fuse, forming a single nucleus. It is an instance of total conjugation, 

 similar to the total fusion in some Monadida, but, unfortunately, the 

 significance of the process and the bearing upon the life-history of 

 the individuals are entirely unknown. 



The union of two individuals within a common cyst is not infre- 

 quently observed among the Gregarinida, and has been a long-known 

 phenomenon. Two or more individuals may join end to end, pro- 

 tomerite to deutomerite, or side to side, and so form aggregates (Fig. 

 27, p. 58). If the individuals thus associated happen to be mature 

 at the same time, they may develop a common cyst and so give the 

 appearance of conjugation. Such pseudoconjugation frequently leads 

 to the formation of catenoid colonies, where the protomerite of one 

 {satellite) becomes attached to the deutomerite of another {frimitc). 



We are indebted to Wolters ('91), Siedlecki ('96, '98, '99), and 

 Schaudinn ('96, '99) for more complete accounts of conjugation 

 among the Gregarinida and Coccidiida. According to the former, 

 two gregarines {Monocystis agilis) place themselves end to end, but 



