HETEROGONY AND EVOLUTION 



217 



This implies that we have a fundamental growth-mechanism 

 controlling size and location of organ, but that its form is 

 capable of modification by numerous independent genes. We 



Fig. 95. — Specific variations in detail of heterogonic organ (cephalic horn) 

 in different species of Goliath beetles (Goliathidae). 

 1 Chelorina polyphemus. 2, Eudicella euthalia. 3, Goliathus giganteus. 4, Mccynorhina torquata. 

 5, Taurina nireus. 6, Stephanorhina guttata. 7, Neptunides polychrous. 8, Taurma Umgiceps. 

 q Trigonophorus delesserti. 10, Rhanzania bertolinii. 11, Myctenstes rhinophyllus. 12, Theodosia 

 magnifica. (1 1 and 1 2 resemble Dynastids in possessing prothoracic horns) . 1 3 and 14, Dicranocephalus 

 wallichii, two views. 



must further suppose that other independent genes are capable 

 of modifying the size-relations (growth-ratio) of the organ in 

 minor quantitative ways. (Fig. 95.) 



