WENRICH: spermatogenesis of PHRYNOTETTIX MAGNUS. 93 



the proximal ends separating and moving about 90 degrees apart, so 

 that a rod-shaped element is formed the middle of which represents 

 the distal end of the original segment. The rod, thus extended, be- 

 comes oriented with its long axis parallel to that of the spindle and it 

 separates in the middle, thus bringing about an equational division. 

 Tetrad "A" also forms rings, but these were not traced into the meta- 

 phase, and their later behavior is not known. 



4. Tetrad " B" occurs in one or the other of two forms: either (1) 

 as an equal pair (in two of the thirteen animals), or (2) as an unequal 

 pair (in the other eleven animals) . The unequal pair differs from the 

 equal in the absence of a large terminal granule at the distal end of 

 one of its members. Both types show the same behavior, opening 

 out at both ends of the segment so that a cross is formed. The 

 separation along the plane of the primary split is the greater and occurs 

 at the distal end; but the cross becomes so oriented on the spindle 

 that the short arms (i. e. the proximal end of the original segment) are 

 attached to the spindle-fibers. Separation in metaphase is therefore 

 along the plane of the secondary split, thus constituting an equational 

 division. 



5. Tetrad "C" occurs in three forms, designated Ci, C2 and C3. 

 Ci is composed of very unequal elements, the larger of which possesses 

 a relatively very large terminal knob or granule that is not present 

 on the other. C2 is a pair with equal members each of which appear 

 to be homologous to the smaller member of Ci. C3 is a pair of unequal 

 elements neither member of which appears to be exactly homologous 

 to the components of Ci and C2. The smaller member resembles 

 those of Co and may be homologous to them. The larger member is 

 midway in size between the two members of Ci. Co and C3 divide 

 equationally in the first maturation mitosis, but Ci divides half the 

 time equationally and half the time reductionally in this first division. 

 When dividing reductionally the two unequal dyads follow the law of 

 chance in their distribution with reference to the accessory chromo- 

 some, which passes to one pole undivided. 



6. Study of the early growth-stages of the first spermatocyte shows 

 that each of the chromosomes of the telophase of the last sperma- 

 togonial division forms a long spirally coiled thread, which uncoils 

 and stretches out to form the leptotene threads of the primary sperma- 

 tocyte. The leptotene threads conjugate side-by-side (parasynapsis) 

 to form the double threads of the pachytene stage. 



7. It was possible to recognize the chromosome-pair A in the 

 spermatogonia as two separate chromosomes (telophases) and to 



