liv INTEODUCTION. 



ouvertes en dessoiis et eii arriere vers le haut," united 

 at their half or at their base. It carries the canda or 

 anal style. 



According to Fieber, the penis lies hid between 

 these walls. Two plates take their rise below the 

 pygophore, and at their internal bases, a variously- 

 formed style occurs. The plates close the entrance of 

 the pygophore, and their base also is closed, outwardly 

 and below, by an undivided valve. In Cicadetta the 

 pygophore takes somewhat the form of a casque or 

 helmet, seen sideways. 



The pygophore of the female has a peculiar structure, 

 being composed of a longish sheath, furnished with 

 a groove of two valves, within which lie the before- 

 mentioned serrated saws. The anal tube is placed at 

 the end of the colesteron, and has its cauda within, 

 whilst the navicular valve is seen at the end of the 

 vaginal sheath. Fieber calls the plates on each side 

 of the interior border of the ventral segments, "lateral 

 plates" (nehen-platten) , but Sahlberg names these 

 " lateral lobes." A better idea of these complicated 

 adjuncts may be got from an inspection of Plates XII., 

 XVIII. and XXI. It must be admitted that the 

 functions of these curious parts of the male pygo- 

 phore are but little understood. Their great diversity, 

 and the wonderful correlation of the male to the 

 female parts cannot be explained on any doctrine 

 either of haphazard, or of conscious selection by the 

 separate sexes. 



Unfortunately, a destruction of specimens is involved 

 in the demonstration of these parts. Their separation 

 is best effected after soaking for some hours in strong 

 potash solution. This reagent has but little action on 

 chitine, whilst it dissolves the soft parts easily. After 

 sufficient washing in water, the parts may be mounted 

 in Canada balsam for the microscope. 



As details will be given on the plates illustrating the 

 various species, no more need here be said ; but 

 Fieber's ' Synopse der Europaischen Deltocephali ' and 



