iqi6] NOTHNAGEL— REDUCTION DIVISIONS 461 



there is a pairing, there is no twisting about of the members; but, 

 instead, the tendency is to assume more elongated forms, such as 

 hooks, rods, or wide U's. One member of each pair passes to 

 a pole, where again there is an end to end approximation, as in 

 heterotypic mitosis, of the 8 chromosomes or the haploid number 

 (fig. 49). The tetrad, or 4 granddaughter nuclei, each containing 

 8 chromosomes, may all lie in one plane, although at times they 

 occupy two planes. 



Discussion 



PRESYNAPTIC AND SYNAPTIC STAGES 



Since the investigation began with the examination of the late 

 telophase of the last division of the sporogenous tissue while the 

 individual chromosomes were still plainly evident, although joined 

 together by anastomoses, it is clear to the author that there is not 

 a pairing of somatic chromosomes in fig. 1, or that a previous 

 approximation has taken place. If such were the case, 8 chromatin 

 groups only would be visible. Even at this early phase the vacuoles 

 are making their appearance along the median longitudinal line. 

 The chromatin bordering these vacuoles could not be called linin, 

 although the later enlargement of these forms the fine chromatin 

 structure (figs. 2-8) that Allen (i), Mottier (21, 22, 23), Stras- 

 burger (30, 31), Digby (7), and others term linin. Furthermore, 

 the heavier masses of chromatin granules are due to the nature of 

 vacuole formation ; for, as they enlarge, a greater amount of chro- 

 matin will be left at the angles between the vacuoles, thus giving 

 rise to the so-called " chromomeres " strung along at irregular 

 intervals on a linin thread. 



Beer (2), Mottier (22, 23), and Mottier and Nothnagel 

 (24) find a single spirem formed from the network, in which condi- 

 tion it enters synapsis; while Allen (i), Gregoire (16), Gre- 

 goire and Wygaert (17), Bergh (3, 4), Yamanouchi (32, 33), 

 Rosenberg (27), and Overton (25, 26) see a pairing of spirems 

 either previous to or during synapsis, this act involving the pairing 

 of somatic chromosomes, presumably maternal and paternal, after 

 which they approximate and at metaphase of heterotypic mitosis 

 separate. Nothing more than an inference or a suggestion has 



