EEVISIOlSr OF ELEODTTNT — BLAISDELL. 25 



It appears to me that the outer lobes (PLate 9, fig. Id) which unite 

 to form the basale are the modified greater part, at least, of the 

 paranal plates. 



There must be a definite law governing the deposition of chitin; it 

 can not be diffusely deposited— at random, as it were — but it nnist be 

 first laid down at certain points, called the centers of chitinization, 

 and from these centers spread, or have inherent limitations; different 

 centers coalescing to form larger sclerites or one continuous whole, as 

 in the prothorax. A simple sclerite would then be one formed by the 

 secretion of chitin about a single center; a compound sclerite from 

 two or more centers. The small but symmetrically arranged sclerites 

 observed in the cuticle of larva? may be cited as simple sclerites. 



It might be assumed that the paranal plate in the female is com- 

 pound ; in the male these centers have become shifted, to form the 

 small paranal plate, and the other to become the lateral sclerite of the 

 basale. 



The origin of the several sclerites in the female genital segment of 

 HydroplvUns may be accounted for in this way — they have not coa- 

 lesced and have been shifted according to the laws governing adapta- 

 tion to function ; during divergence and differentiation under changed 

 conditions of environment these several sclerites fuse — of course it 

 is possible for some to be suppressed, others hypertrophied or 

 even revived — and in this manner produce the apparently simple 

 chitinous valves of the Eleodiini. These suggestions are to indicate 

 a line of investigation in the coleopteral series. 



An examination of the edeagophore of Blaps (Plate 9, figs. 3 and 

 4) Avill be instructive. It will be seen that the apicale is divided 

 longitudinally by a well-marked membranous impressed groove and 

 that the apex is bifid ; the basale is also marked by a similar medium 

 groove. These characters indicate a structural condition somewhat 

 intermediate between the Eleodiini and a more primitive state as 

 suggested by Ili/di-opJi'dus. 



If it be imagined that the apicale of Blaps was completely divided 

 along the groove, and tlie alte not strongly inflexed, the edeagus and 

 its pallium would bear the same relation to the valves as does the 

 edeagus to the valves in Ilydropliilns. There is greater specializa- 

 tion in the Eleodiini than in Ihjdrophlhis or Blaps. 



In Eleodes and other members of the Eleodiini the apicale is fre- 

 quently marked dorsally by a membranous area or groove, and less 

 frequently the basale has an impressed median line. Many species 

 do not normally have this groove and such I consider to be the more 

 highly differentiated, although occasionally it occurs on the apicale 

 even in them, and is then to be considered as an instance of ataoal 

 recersloii. 



