106 



bulletin: museum of comparative zoology, 



autosomes divide along the plane of the longitudinal split which first 

 appeared in the polar spireme of the primary spermatocyte. The 

 second maturation division is therefore an equational division. Figure 



Fig. T. — Polar view, metaphase of second maturation division of Stenobothrus 

 curtipennis. Nine cliromosomes. Tlie monosome is present. X 1450. 



Fig. U. — Polar view, metaphase of second maturation division of Stenebothrus 

 curtipennis. Eight chromosomes. The monosome is absent. X 1450. 



Fig. V. — Polar view of daughter chromosomes, anaphase of first maturation 

 division in Stciroxys trilincata. X 1450. 



Fig. W. — Polar view, metaphase of second maturation division in Steiroxys 

 trilincata. Fifteen chromosomes. The monosome is present. X 1450. 



Fig. X. — Polar view, metaphase of second maturation division in Steiro.vys trili- 

 ncata. Fourteen chromosomes. The monosome is absent. X 1450. 



97 shows the anaphase and Figure 98 the telophase of the second 

 maturation division. 



2. Monosome. 



It still remains to follow the monosome of Stenobothrus through 

 the maturation period. At the end of the growth period this element 

 is plainly composed of two distinct parts (Plate 3, Fig. 52), ftne of 

 which is rounded, has smooth contours, and is vacuolated, while the 

 other is elongated, has a ragged outline, and is granular. In the fol- 

 lowing stage ig) the granular part shortens and becomes more com- 

 pact, meanwhile being bent into a V-shape (Plate 7, Figs. 140-141). 



