ORTHOPTERAN SPERMATOGENESIS 667 



the ends of the univalent components would then suffer a reduc- 

 tion division. 



To this comparatively direct observational evidence must be 

 added the strong presumptive proof that the sister halves of a 

 chromosome remain closely united here as in other generations 

 of cells, and that separation between the parts of a tetrad is much 

 more likely to occur along spaces between whole chromosomes. 

 If this were not. true, and if the annular space of the ring chromo- 

 some and the angle of the V-shaped elements should be the longi- 

 tudinal cleft, then there exists a fundamental alteration in the 

 composition of the chromosome and a wide diversity in the behav- 

 ior of daughter chromatids not only in different species but also 

 in the cells of one organism. From all these considerations it 

 therefore appears highly probable that the rod-shaped tetrad of 

 the late prophase and metaphase of the first spermatocyte repre- 

 sents two spermatogonia! chromosomes joined end to end with their 

 longitudinal clefts continuous. We have therefore to determine 

 the relations of the various forms of the first spermatocyte pro- 

 phase chromosomes to this typical element, and then to trace these 

 into the metaphase of this division, and through the anaphase, 

 in order to establish the fate of the parts of the tetrads. 



c. Forms of prophase tetrads 



There is apparently a great diversity of form in the prophase 

 chromosomes, but while this is true, so far as external configura- 

 tion is concerned, in the fundamental matter of organization the 

 rule is uniformity. In discussing this organization certain ele- 

 ments and relations must be regarded. They may be summarized 

 as follows: number of parts — four chromatids; relationship of 

 parts — one pair of maternal, one pair of paternal chromatids, each 

 pair produced by the longitudinal division of a mother chromo- 

 some, all four homologous; spatial relation of parts — daughter 

 chromatids more or less in contact along the plane by which they 

 were produced from the mother element, homologous chroma- 

 tids united endwise; attachment of spindle fiber — at the same 

 point as in previous generations, as a rule at the point where 



JOURNAL OF MORPHOLOGY, VOL.25, NO. 4 



