NO. I 



THE INSECT HEAD — SNODGRASS 



55 



In further experiments Herbst found that in the Crustacea the 

 formation of an antennal regenerate in place of an eye depended on 

 the destruction of the optic gangHon, otherwise a new eye and eye 

 stalk were regenerated. In the lower vertebrates, however, Goldfarb 

 (1910) reports that the destruction of nerves to an amputated part 

 has no effect on the regenerate ; a salamander thus treated replaces 

 a leg and its tail, a tadpole its tail, and an earthworm its head. 



Considering the many known examples of abnormal growth of the 

 appendages of insects, such as those recorded by Przibram (1910) 

 in adults, and by Cappe de Baillon (1927) in the embryo, nymph, and 

 adult of Carausins morosus, it is difficult to believe that any kind of 

 abnormal growth can have any phylogenetic significance. All such 

 things result from some disturbance of the growth factors, and would 

 appear to have no more meaning than a two-headed rooster or a 

 six-legged calf. I once saw in a circus a three-legged man, but I am 

 not convinced our ancestors were tripods. 



LETTERING ON THE FIGURES 



