Maturation divisions: origin of the tetrads by ring formation in the spermatogenesis of the mole-cricket (<i>Gryllotalpa</i>) (vom Rath). <i>a</i>, primary spermatocyte with six split, bivalent chromosomes. <i>b</i> and <i>c</i>, Split has opened out. <i>d</i>, concentration of
the chromatin has made visible the belated transverse division. <i>e</i> and <i>f</i>, grouping of the completed tetrads in the equatorial plate of the first maturation division.
From E. B. Wilson, <i>The Cell in Development and Inheritance</i>
published 1911
<i>Encyclopædia Britannica</i> (11th ed.), v. 7, 1911, “Cytology,” p. 718, fig. 11.