232 



INTRODUCTION TO CYTOLOGY 



these threads conjugate in pairs side-by-side (parasynaptically ; para- 

 syndetically}. The association does not take place at all regions of the 

 threads at once: it begins at one or two points, commonly at one end, 



FIG. 84. Reduction in sporocyte of Nephrodium. 



A, leptonema. B, recovery from synizesis; parallel conjugation consummated during 

 synizesis. C, pachynema. D, second contraction of bivalent spireme. E, diakinesis. 

 F, anaphase of heterotypic mitosis. G, interkinesis. H, homreotypic mitosis. 7, two 

 of the four spore cells. (After Yamanouchi, 1908.) 



and gradually involves all portions, so that at stages when the process is 

 yet incomplete the two threads may be closely paired at some points and 

 widely divergent at others, giving an appearance very unlike that of the 

 halves of a longitudinally split chromosome in a somatic cell. This is 



