IJHKTRA^EIA KlRKMANl. 15 



the striated area described in the spores of Sarcocystis, could 

 be detected. It differs from a typical Myxosporidium in that 

 spore-formation typically terminates the trophozoite stage, 

 the whole of the trophoplasm being converted into the spores. 

 In two or three cases, however, in about 100 specimens, the 

 whole of the trophoplasm was not involved in the spore- 

 formation. I consider that these cases are to be regarded as 

 a reversion to a more typical Myxosporidium ancestor, where 

 the formation of spores is indefinitely continued. The organism 

 may be regarded as having become adapted to the relatively 

 brief life of its host. 



The so-called " vacuole " at the broader end of the spore 

 recalls the iodinophilous vacuole found in so many spores. 

 In Bertramia kirkmani it shows no particular affinity for 

 iodiue, and it appears to arise from the original nucleus. 



It is interesting, also, to note that ten chromatic masses, or 

 nuclei, are frequently found in the sporoplasm, thus recalling, 

 for example, the ten nuclei which are formed in the pansporo- 

 ])lasts of Myxobolus. 



To conclude, Bertramia kirkmani is to be regarded as 

 being derived from a Myxosporidium ancestor, in which the 

 typical structure and life-history have become modified :ind 

 simplified, in accordance with the special conditions occurring 

 in its comparatively short-lived host. 



EXPLANATION OF l^LATE VI, 



Illustratiug Dr. Ernest Warren's paper on " Bertramia 

 kirkmani sp. nov., a Myxosporidium occurring in a 

 South African Eotifer." 



Fig. 1. — X 20()0 diameters. Yoiuii^-est troiiliozoite found, possesses 

 two nuclei (».) and distinct nuclear membrane (n.m.). 



Fig. 2. — x 2000 diameters. Trophozoite in which the nuclei are in 

 a state of division. (7. Dyaster stage showing achromatic fibi-es. 

 d.n. Daughter nuclei after the disappearance of the achromatic fil^res : 

 the chromatin is extending around the periphery of the nucleus. 



