238 THE CAUSES WHICH PEOPAGATE 



portion, and also encircles the horny pieces in a curve (Plate VI., 

 Fig-. 1). These are noticed by Siebold as brown punctures, and 

 Oscar Schmidt traces their develoj^ment from their rudiments in 

 the larva. 



Herr Vitis Graber, in an intricate paper, seeks morphological 

 harmonies in this organ, noticing in it some obvious variation 

 and degrees of develo2:)ment. He observes, likewise, the anterior 

 denser portion of the drumskin is wrinkled and sometimes 

 hirsute, hairy, or minutely scaly, a feature which vanishes pos- 

 teriorly. Hence he concludes it may be regarded as a modifi- 

 cation of the integument, where these characters are commonly 

 strongly marked. The hairy aspect extends to the arm of the 

 compound horny piece in sj^ecies, which, as, Leydig remarks, is 

 itself at its extremity gradually attenuated, thus passing into 

 the substance of the membrane. The tongue-like projection of 

 this piece in one kind is stated to be hollow, with an exterior 

 orifice. When treated with oxalic acid, the drumskin shows a 

 structure of nucleated polyhedral cells. Herr Yitis Graber like- 

 wise describes the myology in the vicinity of the drumskin, and 

 specifies one muscle as the tensor tympaui. 



Yet, after all, a far readier proof of the function of the 

 auditory organs may be gathered from observation than descrip- 

 tive specialisation and comparison. For if any one will observe 

 the grasshoppers in the meadows, it will be noticed how 

 the malc;, on the conclusion of his music, lowers one or both 

 femora horizontally, retaining the elytra somewhat raised, thus 

 exposing these membranes until he receives a response, or how, 

 when he seeks to allure the female, he places himself so that the 

 stridor shall impinge directly on one or other of her cavities, 

 which she voluntarily exposes by lowering a femur (Plate III., 

 Fig. 8) . The cavities in the latter sex are usually of greater 

 dimensions than in the males, and the drumskin more attenuated. 

 External structures similar, apparently to these, may be ob- 

 served in male cockroaches, laterally, at the hind margin of the 

 metathorax.'^ 



* Regarding the hearing of the Orthoptera; see John. Miiller, Fiir vegleich. 

 Phisio. des Gesichtssin, 1826, p. 438 ; Nova Acta. Acad. Leop. Carol., XIV., 

 p. 157; Siebold, Erich. Archiv. fiir Naturgesch. 18-14, s. 52 — 8i ; Hansen, 

 Gehor hei Locusta, Zeitschr. fiir wiss. Tool. 1866, s. 2 ; also, De Geer, Latreille, 

 Burmeister, Goureau, Kirby and Spence, Landois, Fischer, &c. 



