The ingenious hypothesis propounded by Gegenbaur, that the tracheal tubes of Insects were originally adapted to aquatic respiration, and that the stigmata arose as the scars of disused tracheal gills, has been discussed in chap. [iv]. Semper has suggested[162] that tracheæ may be modified segmental organs, but the most probable view of their origin is that put forth by Moseley,[163] that they arose as ramified cutaneous glands. In Peripatus the openings are distributed irregularly over the body; the external orifices lead to pits, from which simple tubes, with but slight spiral markings, extend into the deeper tissues.
CHAPTER IX.
Reproduction.
SPECIAL REFERENCES.
Brandt, A. Ueber die Eiröhren der Blatta (Periplaneta) orientalis. Mem. Acad. St. Petersb. Ser. 7, Vol. XXI. (1874). [Ovarian Tubes of Cockroach.]
Lacaze-Duthiers. Rech. sur l’armure génitale femelle des Insectes Orthoptères. Ann. Sci. Nat., Zool., 3e Sér., Tom. XVII. (1852). [External reproductive organs of female Orthoptera.]
Berlese. Ricerde sugli organi genitali degli Ortotteri. Atti della R. Acad. dei Lincei. Ser. 3, Vol. XI. (1882). [Genital Organs of European Orthoptera.]