MALE GERM CELLS IN NOTONECTA 79 



to be the case. This process in N. insulata is somewhat similar 

 to that described by Arnold ('08) in Hydrophilus, and by Davis 

 ('08) in some of the Orthoptera. The masses are perhaps 

 comparable with those described in many plant cells as 

 ' prochromosomes.'' 



After the stage of the scattered chromatin masses in N. insulata, 

 a process of absorption sets in. The masses gradually decrease 

 in size and the connecting strands become thicker, especially 

 in the region of the karyosphere (fig. 44). By an absorption of 

 all the chromatin masses, a spireme of approximately uniform 

 thickness is formed which is irregularly coiled about in the nuclear 

 cavity (fig. 45). The spireme is not formed here by an unravel- 

 ing process as described by Janssens, Davis and others, but 

 by a uniform distribution of the chromatin material along the 

 connecting strands. A somewhat similar formation of the lepto- 

 tene spireme has been described by Gerard ('09) in Stenobothrus. 



The spireme now l)ecomes arranged in loops which are more or 

 less oriented toward the karyosphere and may connect with it 

 at their apices (fig. 46). The karyosphere seems to act as a center 

 of acti\dty hke the chromoplast of Eisen and Janssens. Later 

 the loops take up a position on the nuclear wall, receding from the 

 karyosphere which remains in the interior (fig. 47). The loops 

 then become somewhat irregular, coiled and thicker; their stain- 

 ing capacity gradually diixdnishes until in faintly stained prepara- 

 tions only the karyosphere and a few scattered remnants of the 

 loops take the chromatin stain (figs. 48-50). This change can 

 be readily appreciated by comparing these three figures, which 

 are from the same slide. The nuclear cavity is, however, filled 

 with a flocculent reticulum, which is quite faint in lightly stained 

 preparations, but is very noticeable and takes a deep chromatin 

 stain in preparations that are less extracted. 



The foregoing facts in Notonecta are extremely perplexing. 

 Since the spireme is formed from the scattered masses, it must 

 apparently at one time contain the essential elements of the chro- 

 mosomes. A transfer of these elements into the karyosphere 



' These are evidently similar to the 'massive bodies,' recently described in 

 other insects by Wilson ('12), as occurring in Stage b. 



