Note 76 — PART I.—MORPHOLOGY AND PHYSIOLOGY (continued 12)

Nusbaum’s view has been questioned by Heymons, who, from his studies on the embryology of the cockroach (Periplaneta and Phyllodromia), Forficula, and Gryllus, concludes that the ectodermal ends of the sexual outlets owe their origin to an unpaired median hypodermal invagination, and that it is quite doubtful whether the ectodermal portions of the sexual passages of insects were ever paired (p. 104). On the other hand he appears, even throwing out the case of Ephemera, to have overlooked Nassonow’s discovery of paired outlets in the young of Lepisma.