MALE ORGANS OP GENERATION. 213 



lower down, so that the withdrawn penis projects beyond it ; the upper 

 margin of this horny arch is somewhat reflected, and forms two pro- 

 cesses, to which muscles are attached that assist to push the penis 

 forward (PI. XXV. f. 7- a, a}. The second flat longitudinal horny 

 piece lies in the lower part of the bag between the shanks of the arch 

 (PI. XXV. f. 6. 6). If the prepuce be opened we first meet with the 

 horny sheath of the penis, a bilobate organ gently bent from right to 

 left, between the valves of which lies a similarly bent and pointed 

 horny spine. Both valves are closely connected by membranes and 

 muscles, and are themselves enclosed in a membranous sheath (PI. 

 XXV. f. 9. .), which is withdrawn by means of a fine horny bone 

 flattened at its end ; it so lies between the prepuce and the penis that 

 it retains the skin when the muscles push the penis forward. The 

 valves of the penis are thickly beset, upon the bowed inner margin, with 

 long setae, which are placed in a close row, as is also the inner spine. 

 This spine has, similarly to the above-described female ovipositor, an 

 excavated channel., in which lies a fine lancet-shaped bristle ; both are 

 connected together by means of flexible skin and muscles, and between 

 the bristle and the channel is the outlet of the ductus ejaculatorius. 

 This spine therefore is the true penis, and the two valves are its case. 



The penis of Hydrophilus (PI. XXV. f. 11 14.) approaches very 

 closely in many particulars to that of Dyticits. The prepuce here also 

 is a truncated bag, from the upper surface of which the penis projects. 

 In the lower part of the bag lies a broad, shovel-shaped, horny plate, 

 from the margins of which on each side a bone originates, which form 

 the lateral limits of the bag ; upon the upper side, at the end, lies a 

 triangular perforated valve, which forms also the superior valve of the 

 anal aperture, and sends off two free lateral processes to the bone of the 

 lower portion (c, c). The cloaca penetrates beneath this valve, and is 

 separated from the penis merely by a fold of the prepuce. The penis 

 itself consists of the bivalved sheath and the unequal spines lying 

 between them. Upon the inferior side the valve borders upon a heart- 

 shaped horny plate (G), which appears to form the support of the entire 

 organ ; its lateral margins turn upwards, and a coarse skin is attached 

 to it, which closes the canal of the penis from above. The valves (E, E,) 

 of the penis itself are pointed downwards, they are bent, concave, horny 

 bones, which are internally filled by membrane and muscles, which 

 unite to them the central spine of the penis. The most central spine 

 (F. P ; ) is not bivalved. as in Dyficns, but a perfectly closed tube, at the 



