132 Eisen, The Chromoplasts and the Chromioles. 



The chrornoplast stains intensely dark, just like the chromioles, 

 while the lininoplast stains like the liuin granules. There may be 

 one or more chromoplasts, and there may be several lininoplasts. The 

 lininoplasts are nearly always round and are never seen in division, 

 while the chromoplasts are often seen to be in state of direct division. 

 They may be either round or oblong, even or contracted in the centre. 

 In the early stages the chromoplasts lie entirely free from the chro- 

 mioles, surrounded only by a radiating halo of liuiu-threads. As far 

 as mitosis is concerned the cell-stage just described is the one of ab- 

 solute rest. The various constituents of the cell are at this stage 

 simply in a state of metabolism, preparing themselves for the future 

 work of mitosis. The first sign of an ushering in of the latter con- 

 sists in a movement of the chromioles. These are apparently attracted 

 by the chromoplast, and we soon see the chromoplast surrounded by 

 a number of strings of chromioles, for which strings I have proposed 

 the name of leaders. These leaders approach the chromoplasts 

 from all sides and connect with it. 



In the beginning, the number of leaders may be variable, but 

 later on we find that there are as many leaders as there are to be 

 chromosomes in the fully developed nucleus. At the end of this stage 

 we find in Batrachoseps twelve leaders attached to one or two chromo- 

 plasts. All the chromioles are now connected to form leaders none 

 being left free in the nucleus. In the early stage we find that each 

 leader consists of a single row of chromioles, more or less surrounded 

 by a thin film of a distinct and particular chromoplasma - probably 

 derived from the chromoplast - - and strung together by a thread 

 formed of linin granules. 



As the leaders develop we find that the chromioles group them- 

 selves by threes, thus forming incipient chromomeres. The leaders 

 now begin to contract more and more, and at the end of this stage 

 we find in the nucleus, which by this time has become perfectly round, 

 one or more chromoplasts connected with twelve leaders made up of 

 a constant number of chromouiers, each chromomere containing three 

 chromioles. In the next stage of the nucleus the chromosomes become 

 differentiated in the following manner: 



The leaders split lengthwise, but the distal ends remain con- 

 nected with, or rather are held together by the chromoplast. The 

 splitting of the leader is caused primarily by the splitting into two of 

 each chromiole and chromomere. Immediately proceeding the splitting 

 of the leaders the chromomeres each contain six chromioles. This 

 number is constant, and from now on in every fully developed chromo- 

 mere we shwall always find six chromioles. An account of the pro- 

 cess of the formation of the chromosomes is outside of the scope of 

 this paper, but has been fully set forth in the preliminary report men- 

 tioned above. 



