160 BRITISH CICAD.E. 



came over these individuals so suddenly, that they died 

 conjugated, and in that condition they have been pre- 

 served to present times, in the deposits of ancient 

 calcareous mud. 



I have killed, and afterwards digested in an aqueous 

 sohition of potash, conjugated examples of Cixius, 

 Aphrophora, and Deltocephaliis, without causing a dis- 

 union of parts. Although by such treatment speci- 

 mens may be made quite transparent and supple, 

 their apparatus is too complex and intricate ; by reason 

 of the overlying of parts, to allow drawings to be made 

 of the interlacing of the styles. The chitinous male 

 and female parts chiefly assist in keeping a close con- 

 nexion, although in a secondary degree the softer parts 

 do their share. 



I look on these booklets as purposive or adaptive ; 

 for it has been authoritatively admitted "that, although 

 an organ may not have been originally formed for some 

 special purpose, if it now serves for this end, we are 

 justified in saying that it is specially adapted to that 

 end." 



If we exclude purpose or design in the Scheme of 

 the Universe, we are thrown back on spontaneitij or 

 fortuity. If these words be used at all, they must 

 always have a limited sense.* The fragment broken 

 from the rock may be called shapeless, and its form 

 accidental. Such a shape, however, is clearly due to 

 laws of cohesion and conditions of stress. The same 

 piece falling into a swirling torrent may, again by 

 the action of simple laws, become a sphere more or 

 less perfect, through attrition against the bottom. 



The intromittent organs of Aphides, and of most 

 other insects, are usually simple tubes. How or why 

 these parts should assume the complexity seen in many 

 Tettigidse is unknown to us, and mere conjecture will 

 lead to little of scientific value. 



The effects of use and disuse, excitation and undue 



* Aei yap £f TrtTTTot^trtv oi Aio? )tvf3ot. — Soph. Fr. 763, 

 God's work is no mere chance. 



