PYGOFER OF THE TETTIGID^. 161 



rest, struggle and apathy, upon functional organs, 

 muscle, and the like, have been often examjDled. Mr. 

 H. Spencer leans to the belief that functional disturb- 

 ance of the nervous, and other systems, are trans- 

 missible by inheritance. Diminished use often means 

 diminished size, and little exercised parts thus may 

 become rudimentary in these particulars, from what 

 Mr. H. Spencer calls the " inherited effect of changed 

 structure." Atrophy in the jaws, the legs, and the 

 muscles of lapdogs, from the cessation of struggle for 

 obtaining their food, has been recognised ; and many, 

 though not all, biologists will think it proved "that 

 the modified action of a part produces an inheritable 

 effect." Charles Darwin clearly shows, in many 

 instances, that habit, use, disuse, &c., modify both 

 constitution and structure, and if we dismiss "logo- 

 mache," this to most thinkers will appear to be a 

 legitimate conclusion on the main issue. 



We may thus conceive that, under altered circum- 

 stances of life, details of structure can somehow arise, 

 and become permanent ; and Charles Darwin, with 

 reference to the fertilization of orchids, thought that 

 acquired characters might finally become significant 

 through a lengthened natural selection.* 



The penis in Pentatoma shows itself as long, white, 

 silvery, and filiform. In Liburnia guttula it also 

 appears to be somewhat similarly shaped ; or rather 

 the penis is strap-like, and flanked by two bristly 

 threads enclosed in a spatulose sheath. In Idiocerus 

 fulgidus the penis is singularly plumose (Plate XXXI., 

 figs. 2c, 2d). 



No very remarkable divergencies have been noted in 

 Deltocephalus ; but Mr. Edwards has pointed out the 

 complexity of the genitalia in the Typhlocybidae ; and 

 he considers the fixity of forms is such that it may rise 

 to specific value. The penis here chiefly consists of a 

 tubular chamber, with its canal much dilated in the 

 middle. Very generally the apparatus is crooked or 



* See ' Fertilization of Orchids,' p. 288. 

 VOL. II. M 



