684 C. E. McCLUNG 



movement are extended in this direction as split rods. Where 

 the fiber insertion is not terminal, as in Stenobothrus, the rings 

 separate, as longitudinally divided half rings. (6) Davis con- 

 ceives the point of fiber attachment to be permanent from genera- 

 tion to generation of cells, and finds strong confirmation for this 

 idea in the chromosomes of Stenobothrus where there are ter- 

 minal, median and subm.edian attachments. In Steiroxys there 

 are also m.edian attachments, but in the other forms studied 

 apparently they are all terminal. (7) Where the fiber attach- 

 ment is terminal the anaphase chromosomes of the first sperma- 

 tocyte appear as simple V's, but in those cases with median or 

 subterminal attachment the chromosomes are double V's or J's. 

 (8) As a result of his study on the different species of Orthoptera, 

 Davis concludes that the first spermatocyte mitosis witnesses a 

 separation of homologous chromosomes and is therefore a reduc- 

 tion division in Weismann's sense. (9) Further he concludes 

 that in the second spermatocyte the halves of chromosomes, 

 longitudinally split in the first spermatocyte prophase, are sepa- 

 rated by an equation division. 



Buchner ('09), from his investigation of Oedipoda, reaches the 

 following conclusions: (1) The twenty-three chromosomes of 

 the spermatogonium are recognizable as eleven tetrads, plus the 

 accessory chromosome, in the first spermatocyte. (2) The 

 planes of the future longitudinal and cross divisions are recogniz- 

 able in the prophase chromosome, which is an elongated thread 

 with a central cleft representing the position of the future reduc- 

 tion division. This extended thread may be subjected to unequal 

 pressure on the two sides and then takes the form of a U. The 

 free ends of such a tetrad may come into contact and thus produce 

 a ring. In oblique view these rings, which do not lie in one plane, 

 have the appearance of a figure 8. By approximation of the two 

 elements lengthwise and by breaking apart at the ends, parallel 

 rods result. If the forces exert themselves equally on both sides 

 of the tetrad it remains extended. Short elements under these 

 conditions are straight rods, but longer ones may be drawn out 

 at the center and produce crosses with arms of various proportion- 

 ate lengths. Combinations of the two types may occur and 



