pinney: chromosomes of anasa tristis. 359 



(a) shows a rod form in which the division at right angles to 

 the long axis may or may not separate elements of opposite 

 parental origin. It is impossible to ascertain whether these rod 

 forms have passed through the cross stage, since some of the 

 earliest recognizable tetrads have this form and keep it as they 

 condense. 



The manner in which these forms are evolved from two con- 

 jugated chromosomes of opposite sex, each split longitudinally, 

 is similar to that described for the Orthoptera by McClung;* 

 (d) is an unusual condition at this stage of the smallest sper- 

 matogonial chromosomes. Even in stages as late as those 

 shown in figures 22 and 24, plate LXVI, the separate halves 

 of this pair often lie on opposite sides of the nucleus. Just 

 previous to the metaphase they approach end to end. The 

 constriction between the two halves is never obliterated by a 

 close union. Evidently synapsis has had no effect on the 

 smallest two members of the spermatogonial complex, al- 

 though they undoubtedly entered into the synaptic knot. Sub- 

 sequent changes consist in the condensation of these filiform 

 tetrads to form the homogeneous elements of the metaphase. 

 As the chromosomes approximate the homogeneous condition 

 they arrange themselves at the periphery of the nucleus. This 

 tendency may account for the characteristic position of the 

 accessory during synizesis, the growth period and the sper- 

 matocyte prophases. The same nuclear membrane which is 

 formed previous to synizesis continues to function up to the 

 time of a late spermatocyte prophase. At the latter stage 

 there are present within the nucleus thirteen distinct bodies. 

 Figures 10 and 11, plate LXVI, show two parts of the same 

 nucleus appearing in adjacent sections. The thirteen bodies 

 are drawn. These must represent the twenty-one sperma- 

 togonial chromosomes plus the plasmasome created during 

 synizesis. 



Before stating the homologies between these spermatocyte 

 structures and those of the previous generation the history of 

 the accessory will be followed, beginning with synapsis. In 

 this connection the behavior of the new spermatocyte element, 

 the plasmasome, will be reported. The time of appearance, the 

 nature and source of these two bodies, have already been spoken 

 of. It has also been mentioned that immediately after synizesis 

 the two bodies are practically equal in size. In the succeeding 



* McClung, C. E., '00, The Spermatocyte Divisions of the Acrididse, Kansas University 

 Science Bulletin. IX, 1. '02 ; The Spermatocyte Divisions of the Locustidse, ibid., XI, 8. 



