. The descent of man : and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings. 282 THE DESCENT OF MAN. on the undftr side of the nervure of another species of Gryllus, viz., G. domeaticus. With respect to the formation of these teeth. Dr. Gruber has ehown^^ that they have been developed by the aid of selection, n^om the minute scales and hairs with which the wings and body sn e covered, and I came to the same conclusion. Fig. 13. Chlorocoelus Tanana (from Bates). wing-covers. a, b. Lobes oi opposite with respect to those of the Coleoptera. But Dr. Gruber further
. The descent of man : and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings. 282 THE DESCENT OF MAN. on the undftr side of the nervure of another species of Gryllus, viz., G. domeaticus. With respect to the formation of these teeth. Dr. Gruber has ehown^^ that they have been developed by the aid of selection, n^om the minute scales and hairs with which the wings and body sn e covered, and I came to the same conclusion. Fig. 13. Chlorocoelus Tanana (from Bates). wing-covers. a, b. Lobes oi opposite with respect to those of the Coleoptera. But Dr. Gruber further shows that their development is in part directly due to the stim- ulus from the friction of one wing over the other. In the Locustidse the opposite wing-covers differ from each other in structure (fig. 13), and the action cannot, as in the last family, be reversed. The left wing, which acts as the bow, lies over the right wing which serves as the fiddle. One of the ner- vures (a) on the under surface of the former is finely serrated, and is scraped across the prominent nervures on the upper sur- face of the opposite or right wing. In our British Phasgonura viridissima it appeared to me that the serrated nervure is rubbed 36 'Ueber der Tonapparat der Locustiden, ein Beitrag zum Darwin- ismus,' 'Zeitsch. fur wissensch. Zoolog.' B. xxii. 1872, p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882. New York : Merrill and Baker
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