286 CKNEKAL REMARKS. 



As a rule, then, the orders having indirect modes of 

 development do not show to any marked extent accel- 

 eration in the inheritance of adult or adolescent 

 (pupal) characters, but, on the contrary, the char- 

 acteristics of these later stages remain remarkably 

 constant in the ages at which they are inherited. 

 They do not encroach upon or replace the larval 

 stage to any very marked extent, as in the examples 

 cited above, among the Orthoptera or Hemiptera. 

 This might be considered as fatal to the application 

 of the law of acceleration, and this would be the case 

 if that law were anything more than the expression for 

 a general result of causes which underlie the action of 

 heredity. One of these causes is what we have al- 

 ready expressed as a law of replacement. 



Two modifications cannot occupy the same space, 

 and the secondary larval forms having become fixed 

 in the organization, they hold their own in the devel- 

 opment of individuals against the encroachment of 

 the pupal and adult characters by virtue of their suit- 

 ability and the conservative power of heredity. The 

 few cases in which acceleration of the pupal stages at 

 the expense of the larval stages does take place in 

 the second series of orders seem to show this, since 

 they occur not in the normal forms having the ordi- 

 nary habitat, but in parasites like the Pupipara. 



Teachers who read Sir John Lubbock's interesting 

 chapter on the Nature of Metamorphoses {Joe. cit.) will 



stage, and are in reality, although wingless, comparable with 

 active pupce. In the case of the sexually perfect forms which 

 emerge from pseudova, they are, according to Comstock, in a 

 still more advanced condition. 



