— co- 

 in the first stages of division the dividing' individual has 

 one nucleus of a round shape lying deep in the endoplasm. 

 There is neither an undulating membrane, nor axostyle with 

 the nucleus, and the latter exhibits some characters of the 

 beginning division. I am sorry that I was not able to clear 

 the question as to what becomes with the membrane of the 

 maternal individual before division, and with the axostyle, if 

 present. These organoids possibly become absorbed. 



The division of the nucleus follows on the lines recently 

 described in Tetramitidae and Hypermastigina, and 

 which Janicki (18) proposed to name Grassi's type of di- 

 vision. The latter is characterized by the spindle situated 

 externally to the nucleus du.ring the nuclear division, and by 

 the preservation of the nuclear membranr^ in all the stages 

 of division. 



The earliest stage of nuclear division observed by me has 

 the following aspect (tab. II, fig. 23). The nucleus has the 

 usual spherical shape and contains the karyosome split in 

 two parts amongst numerous granules, which lill up the 

 nucleus. The nucleus is clasped by an arcuate spindle closely 

 adjoining its membrane. The spindle stains intensely with 

 Heidenhain's haematoxylin and has a fibrillar structure. The 

 spindle terminates in small knobs, which prove to be two 

 centrioles. I did not succeed in stating exactly from where 

 the spindle originates. 



The further progress of the nuclear division was investi- 

 gated by me in detail. The karyosome becomes lighter and 

 is absorbed, Avhilst the nucleus growls in length, (tab. Ill, fig. 

 27). Twice I saw thin curve'd threads extending from the 

 ends of the spindle in this stage, these threads become 

 thinner and terminate in the endoplasm. The significance of 

 these threads remains unsolved (remnants of the undulating 

 membrane of the maternal individuals?). Then the interior of 

 the nucleus becomes filled up with a great number (over a 

 hundred) of rather large, round chromatin grains— the chro- 

 mosomes (tab. II, fig. 26). The nucleus becomes oval, and the 

 chromosomes elongate and assume the shape of threads (tab. Ill, 

 fig. 30). It is difficult to state whether they split longitudinally 

 or not, but they soon become arranged into two groups, all 

 the chromosomes being directed with one of the ends towards 

 the middle of the nucleus, and with the other to one of the 



