Abstract
1. In Stomaphis yanois the smaller secondary spermatocytes divide, and develop to some extent, but retrogress to spherical cells. 2. In Neothomasia populicola and Macrosiphum ambrosia, cases of division of the smaller secondary spermatocytes were found, but no developing smaller spermatids were observed. 3. In Neothomasia populicola and Macrosiphum ambrosia spherical cells like those in Stomaphis yanois were found in the cysts containing spermatozoa. These were identified as retrogressed larger spermatids.

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