The Presidenfs Address. By the Eev. W. H. Bollinger. 203 



earlier activity in the nucleus. That is to say, that the plexus-lihe 

 structure condenses or congregates at one end of the nucleus, so 

 that there is a rapid transition from the condition of the nucleus 

 seen in tig. 13 to the condition seen in fig. 14, where at a the 

 hyaloplasm is clear, while &i c d there is a thick gathering of what 

 had before filled the whole nuclear contents, as at fig. 13. At the 

 same time a faint division appears in the long axis of the nucleus, 

 as at a h, fig. 14. And now it is that the amoeboid condition of 

 the whole body-sarcode begins and the process of fission rapidly 

 proceeds. 



With the splitting of the four flagella into two pairs (plate IX. 

 fig. 2 a) there is a visible incision in the nucleus h, ibid. ; this 

 condition of the nucleus is shown at fig. 15, where the faint axial 

 line seen at a h, fig. 14, has become strong and beaded ; and two 

 delicate beaded cords proceed from the plexus on each side to 

 this strong line of cleavage, as seen at e e. In fig. 16 the 

 process of division is more than half accomplished, and the fine 

 beaded lines still retain their relative positions, as at // g. At 

 this point the division of the body of the organism is about half 

 accomplished, and the nuclear fission is complete before the body 

 divides. In plate VIII. fig. 17 we see the two nuclei a moment 

 prior to actual separation; and in fig. 18 we have the nucleus a 

 moment or two after total separation, in which it is plain that the 

 plexus-hke structure is again difi'using itself evenly over the nuclear 

 contents. 



The rapidity and continuity with which these fissions take 

 place are remarkable. In a thoroughly healthy, vigorous field of 

 Tetramitus rostratus from ten to twelve fissions will be efiected in 

 one hour if we steadily follow one of the two divided organisms 

 successively in continuous divisions. There is but little interval 

 between the complete separation of one divided organism from its 

 fellow and the appearance in it of the earliest stages of the next 

 fissional process. And this will continue for hours without cessa- 

 tion, causing a prodigious increase of the organism. It was ex- 

 tremely difficult indeed in some of these organisms to follow to 

 the end this terminal act of fission and to demonstrate the relation 

 borne by the last segmented forms to the genetic fusion and pro- 

 duction of germs, which has been proved to characterize each of the 

 specific organisms when exhaustively studied. They all divide 

 rapidly by fission, and in the same field, without the slightest change 

 or addition, there arise at given intervals forms that slightly differ 

 from the prevailing form, and these go into a state of conjugation 

 resulting in a still sac that ultimately pours out myriads of germs. 

 But I have in three cases been able to see with completeness at 

 what point the process of fission ceased and the genetic state arose. 



I select two instances, both being nucleated forms. The first 



