GRADIENT-FIELDS IN POST-EMBRYONIC LIFE 



361 



Experimental evidence in support of the view that age is concerned 

 is provided by the fact that if the antennae of Dixippus are ampu- 

 tated in the first instar they regenerate as antennae, but if they are 

 amputated in later instars, they regenerate as leg-like organs. Mean- 

 while Sphodromantis provides evidence supporting the view that 

 the effect is correlated with general metabolic activity. In this form, 

 an amputated antenna will regenerate as an antenna if the animal is 



Fig. 174 

 Diagram to illustrate serial heteromorphosis. In Palaemon (above) removal of the 

 eye without removal of its ganglion {a, distal cut) leads to regeneration of an 

 eye {h) ; with removal of the ganglion {a, proximal cut), to that of an antenna-like 

 organ (c). In Mantids (below) amputation of the antenna in the region of the 

 flagellum {d,I) leads to regeneration of a fresh flagellum {e) ; in a basal joint (d,III), 

 to that of a leg (/). (From Przibram, Handb. nor?n. u. path. Physiol, xiv (i), (i).) 



kept at 25° C, but at lower temperatures a leg-like organ is formed. 

 These heteromorphoses are thus presumably produced when the 

 main gradient of the animal is flattened. The flattening would 

 be primarily due to age, but can be accentuated by external con- 

 ditions. The function of these heteromorphoses is of great 

 interest. (Lissmann and Wolsky, 1933.) 



Another main gradient of the early vertebrate embryo is the 

 asymmetry-gradient (Chap, iv, p. 77), which is responsible for the 

 asymmetrical disposal of the heart and viscera. Further evidence 



