1915] Kofoid and Clirisliaiiscn: On Giardia >in(rif! (Grassi) 39 



The prophase may be regarded as the period prior to the forniatiou 

 of the equatorial plate, the metaphase as the separation of chromosomes 

 in this plate, the anaphase as the period of their polar migration, and 

 the telophase as that of nuclear reconstruction. "We \vill now follow 

 the history of each organelle through these periods. 



The blepharoplasts divide (pi. 5. figs. 8, 7, 6) simultaneously, 

 spreading the head of the axostyle and forming between the migrating 

 daughters a new chromatic band. The.se lie athwart the heads of the 

 daughter axostyles as they part and at no time take any part in spindle 

 formation as does the paradesmose in triehomonads. 



The axostyle divides immediately after the blepharoplasts and 

 splits lengthwise from the anterior end posteriorly, .splitting the basal 

 granule, and each daughter taking one of the two posterior flagella 

 (pis. 5. G. figs. 6-17). This process completes the organelles of the 

 two component cells, but it is also the initial step in the division of 

 the individual. It is the last organ to divide in the triehomonads and 

 its behavior here is an indication of the evolution of Giardia from 

 a unicellular type of trichomonad affinities, in which a binucleate 

 somatella with undivided axostyle has come to be the normal 

 trophozoite individual. 



The flagella arise, not by splitting, but by new outgrowth from the 

 lilepharoplast. though none has been figured. The new flagellum 

 follows the path established by the intracytoplasmic shaft of the old 

 one and emerges at its side. It is difficult to determine whether or 

 not this is outgrowth or splitting, but it appears to be the former. 

 The intracytoplasmic part of the posterior flagella, the axostyle, is 

 reproduced by splitting. The distinction between the two methods 

 seems to have no morphological significance. The first flagellum to 

 divide is the antero-lateral which forms a new anterior ehiasma. the 

 inner flagellum being the new one in each case (pi. 5, figs. 5, 6. 7). 

 The emergence of the new flagellum at the surface seems to be delayed 

 till after nuclear division. 



No case of the division or new outgrowth of the intracytoplasmic 

 part of the postero-lateral flagellum has been observed in our material, 

 nor has the formation of new ventral flagella been found in progress. 

 They are fully formed prior to plasmotomy (pi. 7, fig. 33). The pos- 

 terior flagella, originally a pair from the tip of the single axostyle, 

 become doubled sooner or later during mitosis ( pi. 5, fig. 10), but this 

 may be long delayed (pi. 6, fig. 29). 



