THE SPOROZOA 311 



from that of the multinuclear trophozoite, except that its smooth contours 

 are exchanged for a lobulated outline (Fig. 124). According to Bertram's 

 observations, the sausage -shaped morula may now break up into its 

 component cells or spores, which become scattered in the body -cavity of 

 its host. The parasites observed by the present writer, however, were 

 seen to round themselves off and assume a spherical form, a tough cyst- 

 membrane then being formed round the whole mass (Fig, 124,/). Bertram 

 also observed cysts in a single case. As the parasiteg are quickly fatal to 

 their host, it is highly probable that rapid endogenous multiplication is 

 effected by breaking up of the sausage-shaped morula and liberation of 

 the spores without encystment, and that in other cases a protective cyst 

 is formed. There appears to be no difference whatever, however, in the 

 spores in either case, each spore being a small rounded uninucleate cell, 

 limited by a delicate membrane. The spores are set free by the death 

 and disintegration of the host, and are then swallowed by other Rotifers. 

 In some way which has not been observed the spores pass from the gut 

 into the body- cavity, and each becomes the starting-point of a fresh 

 generation of the parasite. All stages of the parasite hitherto seen are 

 perfectly motionless. 



In B. capitellae the morula becomes encysted, and the contents of the 

 cyst are divided up into compartments by trabeculae extending from the 

 cyst-wall, formed apparently from residual protoplasm not used up to 

 form spores. The alveolar condition of the cyst may be compared with 

 that seen in Sarcosporidia. 



Genus 2. Haplo [Aplo-]sporidium, Caullery et Mesnil, 1899, for H. 

 heterocirri, C. and M., parasite of the body -cavity of Heterocirrus viridis ; 

 and H. scolopli, C. and M., parasite of the intestinal epithelium and 

 perivisceral sinuses of Scoloplos mulleri. As in the last genus, a small 

 uninucleate corpuscle becomes by growth and multiplication of nuclei the 

 full-grown, multinucleate, but still unicellular trophozoite, measuring 

 100-150 fj. in length by 20-30 ^ in breadth. The body then becomes 

 segmented into a "morula" of uninucleate cells. In H. scolopli each 

 cell of the morula gives rise by further division to four uninucleate spores, 

 but in H. heterocirri each segment of the morula becomes a single spore. 

 In both cases the spores are distinguished from those of the preceding 

 genus by the possession of a cap or operculum at one pole of the tough 

 envelope, so that the spore resembles to a certain extent a poppy- 

 capsule. In sea-water the operculum opens and sets free the contained 

 sporoplasm. 



Genus 3. Coelosporidium, Mesnil and Marchoux, 1897, for C. chydori- 

 cola, M. and M., from the body-cavity of Chydorus sphaericus. A uni- 

 nucleate corpuscle grows into a multinucleate, sausage -shaped body, 

 60-100 fi in length by 15-20 /A in breadth, enveloped in a thick mem- 

 brane, and containing centrally - placed fatty globules and refringent 

 granules. Later the protoplasm becomes divided into segments corre- 

 sponding with the nuclei, and forms eventually a cyst containing numerous 

 spindle-shaped uninucleate spores. In addition, the spore-formation there 

 appears to be an endogenous cycle, in which the protoplasm contains no 

 refringent globules. The parasite castrates its host. 



