1919] Kofold-Swezrj : Lcidyopsis sphacrica 107 



The nucleus of Lcidyopsis is furtlier distinguished by the presence 

 of a small, coiled chromatin rod similar to the heterochromosome of 

 Trichanympha campanula. This is isolated in a small, clear vesicle 

 at one side of the central chromatin mass and partially imbedded 

 within it. 



BINARY FISSION 



The process of binary fission in Leidyopsis sphaerica shows a 

 close similarity to the various phases of binary fission in Tricho- 

 nympha campmmla. It is characterized bj' the longitudinal division 

 of the centroblepharoplast complex and of the eetoplasmic structures, 

 the formation of a paradesmose, precocious, longitudinal splitting 

 of the chromosomes and pseudosynapsis. Owing to the scanty num- 

 bers of these flagellates which have been present in any one host, we 

 cannot present the full details of the different stages. The close 

 similaritj' between the phases that we have secured and those of 

 the other species, however, would seem to suggest that the remaining 

 stages of Lcidyopsis are also similar. In the following discussion, 

 therefore, the different phases are interpreted in the light of our fuller 

 knowledge of the mitotic phenomena of Trichonympha. 



Division op Ectoplasmic Structures 



The first evidences of division in the extranuelear structures of 

 the body are found in the centroblepharoplast. This structure divides, 

 beginning at the base and splitting longitudinally to the tip. The 

 basal masses become separated into two equal parts (pi. 13, figs. 12, 

 13), taking with them their attached fibers and motor organelles. 

 This divides the entire ectoplasmic layer, leaving a constantly increas- 

 ing strip of endoplasm between them as they move apart. As the two 

 halves of the centroblepharoplast separate, a broad band, the parades- 

 mose, is formed between them (pi. 13, figs. 15, 16). This is attached 

 directly to the bases, leaving the tubular portions of the centroble- 

 pharoplasts standing out from it at right angles, or nearly so. In 

 figures 15 and 16 these parts are omitted, as the structures are viewed 

 from the posterior end of the organism and show the relations of the 

 paradesmose and the basal lobes of the centroblepliaroplasts. Here, 

 as in Trichonympha, with the final separation of the tips of the centro- 

 blepharoplast, each half develops into a tube similar to the original 

 structure. This seems to take place immediately after separation of 

 the halves. 



