62 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
tangled and lack definite arrangement. This condition, which may 
be called early leptotene (fig. 28), is followed by a later leptotene 
(fig. 29), in which the threads become oriented with one end attached 
at one side (the polar side) of the nucleus. Soon there appear among 
the single threads others which are double and twice the width of the 
single ones. The proportionate number of double threads gradually 
increases until all the threads appear double. The stage during which 
the doubling takes place (fig. 30, 31) is the zygotene stage of Grégoire 
(07). When all the threads have become double the pachytene stage 
(Winniwarter, ’00) has been reached (Plate 3, fig. 32-34). This term 
continues to be applicable throughout the relatively long growth- 
period, and until the spireme! breaks up into the haploid number of 
segments, which become tetrads. The number of pachytene threads 
seems to be much less than that of the leptotene threads. 
The stages characterized by the appearance of separate segments of 
the spireme may be designated by the term diplotene of Winniwarter 
(00). This term is used for the sake of consistency with the others 
employed, although the conditions in Phrynotettix differ somewhat 
from those described by Winniwarter for mammals. He describes 
the longitudinal split as disappearing in the pachytene stages, on 
account of the threads becoming twisted, and reappearing in the diplo- 
tene stage. In Phrynotettix the longitudinal split remains visible 
and little or no twisting occurs. 
Soon after becoming independent, a second longitudinal split occurs 
in the spireme segments at right angles to the first, thus forming 
typical tetrads, each composed of four chromatids (McClung, ’00). 
The first longitudinal split, which persists from the pachytene stage, 
may be called the primary split, and the one at right angles to it may 
be called the secondary split. From the time of their formation until 
the succeeding metaphase, the tetrads undergo a gradual shortening 
and thickening. During this period they pass through the well- 
known figures, X’s, K’s, 8’s, rings and crosses (Plate 3, fig. 38). The 
stage during which these changes occur is frequently referred to as 
the diakinesis stage (Hacker, 95%), but it may be simpler to call it 
the postspireme stage (Grégoire, ’07), or the tetrad stage.” 
The postspireme stages end with the establishment of the tetrad- 
1 The term spireme will be used to embrace the stages included under the names leptotene, 
zygotene, and pachytene without, however, implying anything as to the existence of a con- 
tinuous thread. 
2 I have avoided the use of the term, prophase, in connection with the postspireme stages 
because it might properly be applied to the whole series of stages from the preleptotene to the 
metaphase. 
