694 C. E. McCLUNG ' 



tetrads are dumb-bells; (fig. 125 seems, however, to show 

 rings very clearly). (4) All chromosomes lie with their longi- 

 tudinal axes parallel to that of the spindle. (5) A mere separa- 

 tion of the dumb-bells marks the changes in the metaphase. 

 (6) Fiber attachment is not discussed, but from the figures it 

 appears to be terminal. (7) The forms of the anaphase chromo- 

 somes are not described or clearly figured. (8) In the first sper- 

 matocyte a segregation, or reduction, division occurs. (9) After 

 a complete rest stage the chromosomes of the second spermatocyte 

 appear and divide, presumably equationally. 



Wassilieff ('07) says that in Blatta germanica the unreduced 

 number of chromosomes is 23, of which one is the unpaired acces- 

 sory chromosome. By some means, not fully explained, the 

 haploid group of 12 chromosomes is produced from the chromatin 

 of the nucleus resulting from the last spermatogonial division; 

 (in explanation of fig. 37, rods are described as being chromatin 

 segments conjugated end to end). One of the twelve behaves 

 in many ways like a nucleolus and later passes undivided to one 

 pole of the first spermatocyte spindle. The first spermatocyte 

 prophase chromosomes have the form of rings or V's which are 

 produced by the bending of a longitudinally split, transversely 

 cleft thread upon itself. The two segments are separated at 

 this cross division in the first spermatocyte, which is therefore a 

 reduction division. Along the longitudinal split occurs an 

 equation division in the second spermatocyte. 



Morse ('09) records the consistent phenomena apparent in 

 four genera of Blattidae. Among his observations the following 

 of interest in the present study may be noted: (1) The chromo- 

 somes of the first spermatocyte are derived from the spermato- 

 gonial series by a parasynapsis of homologous members, leaving 

 an unpaired accessory chromosome. (2) By an enlargement 

 of the interchromosomal space rings are produced, but persistent 

 rods also occur. (3) Condensation and contraction of these result 

 later in the production of similar forms in the metaphase. (4) In 

 the spindle the rings are arranged parallel with its axis; rods lie 

 in the equatorial plate. (5) Annular chromosomes divide directly 

 into half rings or V's after more or less approximation of the two 



