12 ERNEST WARREN. 



(2) The formation of tlie spore. — The wall of the 

 trabeculfe becomes the spore-membrane ; the nucleus has a 

 somewhat irregular outline. The chromatin becomes concen- 

 trated towards the periphery (figs. 9 and 16, n), and ultimately 

 separates from the nucleolar element either in the form of a 

 band or of a hoop (fig. 18). There appears, however, to be 

 no inherent difference in these ; for in either case the band 

 or hoop divides into two directly without mitosis (fig. 18), 

 and ultimately into six, eight, or ten (figs. 4 and 8) masses 

 of chromatin, which stain readily with safranin or h^ema- 

 toxylin. The vesicle or " vacuole " which remains (fig. 19, v) 

 does not stain at* all readily ; iodine has no particular effect 

 on it, neither has it any marked affinity for aniline stains or 

 haematoxylin. A minute granule can generally be found in 

 the vacuole towards the more rounded end of the spore 

 (fig. 19, g). The sjDore-membrane has a kind of operculum at 

 the narrower end {I), and such may be seen in many Myxo- 

 sporidium spores. Doubtless the young sporozoite escapes 

 through the operculum. 



Fig. 19 represents a ripe spore. In the sporoplasm can be 

 seen some ten nuclei, each surrounded by a clear area, and 

 the " vacuole '*' is situated towards the broader end. 



Average length of spore is 6'1 /i and breadth 2'9 fx; the spore 

 is slightly curved or falciform in shape, thus recalling the 

 spore of Sarcocystis. 



(3) Life -hi story of the species. — Several infested 

 rotifers were kept alive in a small bulk of water and ex- 

 amined daily. The following is an account of one specimen. 

 On July 5tli the rotifer contained about fifteen of the para- 

 sitic bodies, which were of various sizes, the averag'e of four 

 of the largest being about 60 ju in length and 18/i in breadth. 

 The outer border of the bodies consisted of hyaline proto- 

 plasm ; internally they were slightly granular. 



On July 6th the number of the bodies had increased by 

 plasmotomy to about 25. 



On July 7th the bodies were becoming opaque, owing to 

 the development of granules in the protoplasm. 



