416 - Multicellular Animals, Especially Man 



Fig. 22-10. A, the thoracic part of the pupa, cut away from the head and abdomen, 

 remains alive for several months, but does not undergo metamorphosis. This part contains 

 the prothoracic glands, which produce a "metamorphosis hormone," but the glands 

 remain inactive unless stimulated by another hormone secreted by the "brain" (cerebral 

 ganglia) of the insect. B, similar thoracic part into which living brain tissue has been 

 implanted. This part has developed its adult characteristic. C, abdominal part of the pupa, 

 isolated from the thorax and head. This part does not develop, though it does remain 

 alive. D, abdominal part after implantation with both brain tissue and prothoracic glands. 

 Note the development of adult structure (compare with Figure 22-9.) (Courtesy of 

 Carroll M. Williams, Harvard University, and the Scientific American.) 



