Fig. 52. Chromosomes (diploid) of D. ampelophila. The sex chromosomes are XX in the female and XY in the male. There are three other pairs of chromosomes.
<a href="//commons.wikimedia.org/wiki/Thomas_Hunt_Morgan" title="Thomas Hunt Morgan">Thomas Hunt Morgan</a>
1916
<a rel="nofollow" class="external text" href="https://www.gutenberg.org/ebooks/30701"><i>A Critique of the Theory of Evolution.</i></a>, available freely at <a href="https://en.wikipedia.org/wiki/Project_Gutenberg" class="extiw" title="w:Project Gutenberg">Project Gutenberg</a>