ORTHOPTERAN SPERMATOGENESIS 709 



this aspect when studied from the same position. Rings, rods 

 and V's all look alike when viewed from the spindle axis in the 

 equatorial plate. This is not a mere superficial resemblance 

 but represents fundamental community of structure. In every 

 case the cross is the result of the approximation of four chroma- 

 tids in such a way that each chromatid is bent upon itself at right 

 angles and so set that this angle is one of four grouped about a 

 center. This center appears as a diamond-shaped opening, 

 in favorable cases, but in the metaphase is usually apparently 

 obliterated. The arms of the cross to which the fibers attach 

 are approximately straight but the remaining two may be bent 

 in any degree, even to the formation of rings. 



Because the cross comes into view from the lateral aspect of the 

 mitotic figure, it is common in the illustrations of many papers. 

 De Sinety ('01) shows such chromosomes in figures 87, 88, 110, 

 124, 131 and 137; Baumgartner ('04) in figures 13, 14, 16, 18 

 and 19; Moore and Arnold ('06) text figure; Pinney ('08) in fig- 

 ure 24; Buchner ('09) in figures 49, 51, 52 and 55; Granata 

 in his text figures d and e; Nowlin ('08); ('13), figures 15, 

 18 of plate 29, figures 3 and 4 of plate 30, figures 25, 26 of 

 plate 31, figures 19 of plate 32; Carothers ('13) in figures 29, 

 30, 31 and 47. 



By most investigators these metaphase tetrads are represented 

 objectively as they present themselves in stained preparations. 

 Their interpretation depends upon a knowledge of their structure 

 gained from the prophase, and by most students of the Orthop- 

 tera they are conceived to be the four armed figures with a cleft 

 the length of each arm, apparent in the prophase but obscured 

 by the concentration of the metaphase chromosomes. De Sinety 

 ('01), however, in his figure 124 a, represents a cross of two super- 

 imposed, independent chromosomes lying over each other at right 

 angles. Similarly, Brunelli ('11) in figures 12 and 13 shows 

 crosses thus constituted. Both of these authors unconsciously 

 represent the cross correctly, de Sinety in his figures 124 c, 131 

 and 137, Brunelli in his figure 14. The practical unanimity of 

 opinion on this very clear question makes any further discussion 

 of it unnecessary. 



