ACKED. 49 



existence: the advantages are scattered and compensated 

 by disadvantages. 24 



In connection with the objection stated in the preceding 



paragraphs is that specially pressed by Wolff, although long 



Numerous use- a & strongly stated by Mivart, 25 and one that 



fal characteris- has long appealed strongly to me particularly in 



tics useful only - , ,*-.. ,. 



in highly per- connection with the study of the utility of 

 fected state, colour and pattern among insects. This ob- 

 jection is, that numerous useful characteristics or adapta- 

 tions of organisms are useful only in a highly perfected 

 state, often involving a complex and considerable structural 

 development of old (then much modified) or quite new parts, 

 and hence could not have arisen by gradual modification by 

 the selection of slight variations. Darwin himself says that 

 if a single complex organ can be referred to whose full de- 

 velopment cannot possibly be explained through numerous 

 small successive modifications, then his theory must indubi- 

 tably fall. For example, the electric organ of the torpedoes, 

 the brood-sacks or cells on the back of Pipa dorsigera, the 

 chameleon's tongue, and many other organs can be recalled 

 which could not possibly exercise their particular advanta- 

 geous function in an undeveloped and beginning state. In 

 my own eyes has for long stood the familiar case of the 

 mimicry of our common American monarch butterfly, 

 Mimicr of dnosia plexippus, by the viceroy butterfly, 

 Anosia by Basilarckia archippus. The viceroy belongs to a 

 group of species in which the prevailing (almost 

 certainly the ancestral) colour and pattern are white and 

 black (or iridescent purplish and bluish) arranged as a broad 

 white continuous transversal bar across both fore and hind 

 wings, on a black (to purplish) ground. The colour and 

 pattern of Anosia are radically different; brick-red ground, 

 black longitudinal lines following the veins and small white 

 spots in an irregular black submarginal band. Examine the 

 viceroy butterfly. You find no suggestion of typical Basi- 



