62 B. F. LUTMAN. 



It may be that the stage of synapsis is much shortened in the 

 caddis-fly and that of the spireme is correspondingly lengthened. 



The spireme now breaks up into chromosomes and these lie in 

 the nucleus as long slender paired bodies (Fig. 22). The chromo- 

 somes now come to have the peculiar shapes such as X's, Y's, 

 twisted figures, etc., characteristic of the stage of the reduction 

 division (Fig. 23). These soon shorten into the tetrads (Fig. 24). 

 The tetrads take on the typical lozenge form and sometimes show 

 an opening in their center. The manner in which these bodies 

 arrange themselves on the spindle could not be definitely deter- 

 mined as they are small in size and the four segments of the 

 lozenge are all of about the same length. 



The metaphase shows a sharp pointed spindle with its extremi- 

 ties in a centrosome just inside the plasma membrane (Fig. 25). 

 The telophase of this division shows the chromosomes pulled 

 about two-thirds of the way back to the centrosome and the 

 nuclei still connected by the remains of the central spindle (Fig. 

 26). The centrosome at this time is still apparently divided and 

 the rays from it extend down to the cluster of chromosomes. 



The second division, following almost immediately, has little 

 to distinguish it in the metaphase from the first except in its size 

 and in the size of its chromosomes (Fig. 29). In the telophase of 

 this division the centrosome was not to be found just what had 

 become of it has not been ascertained. The remains of the cen- 

 tral spindle is the most conspicuous feature of this stage. The 

 chromosomes seem to spread out at once, as soon as a nuclear 

 membrane is formed, and make the ordinary reticulated network 

 of a resting nucleus (Fig. 34). 



There is a period of growth after the reconstruction of the 

 nucleus, such as Paulmier (n) and other authors have described, 

 followed by a stage in which the nucleus shrinks. Even before 

 the chromosomes are entirely distributed and while they are still 

 present as little pieces of chromatin (Fig. 34), the cell begins to 

 lengthen and the axial filament to form. In fact the long drawn 

 out form of the cell which it has from the last division does not 

 seem to change but passes over at once to the young sperm. 

 The transition stage takes a long time for its completion and any 

 number of transition stages can be found. The chromatin col- 



