Because all the intersegmental muscles of the 2nd segment invariably 

 break down during pupation it seemed probable that the 2nd ganglion lacked 

 the ability to „protect" muscles from histolysis. A ganglion innervates muscles 

 in the segment posterior to its олуп so it was of interest to remove the 2nd 

 ganghon and see if there was any degeneration in the muscles of the 3rd 

 segment. This experiment was carried out with S. cynthia. The results were 

 clear. Removal of the 2nd ganglion 

 caused the muscles of the 3rd segment 

 to degenerate. The results were the 

 same as those obtained by removing 

 the 3rd ganglion. 



The details of the innervation of the 

 muscles are not known but an obvious 



L D 



abc 



4 о 4 4 



4 4 4 4 







4 4 4 4 



4 4 4 14 



IV 



VI 



Actios selene 



Anlheraea рггг.у; 



Samia cynthia 



A Antheroeo pern yi В 



f 



G G о 

 4 14 4 

 4 4 4 

 4 4 4 



Fig. 2. Normal pattern of lateral (L) 

 and dorsal (D) inuscle bands in the 

 pupa of Actias selene, Antheraea per- 

 nyi and Samia cyntlda. (The numbers 

 — 4 indicate amounts of muscle. = 

 = complete degeneration, 4 — normal 

 muscles). 



IV 

 V 



VI " 

 Actios selene 



Fig. 3. Results of removal of abdominal 

 ganglia from fully growTi larvae of An- 

 theraea pernyi and Actias selene. The 

 ganglia removed are indicated by a gap 

 in the nerve cord and the state of the 

 pupal muscles is indicated by the same 

 code as used in fig. 2. 



contribution to the innervation of any segment is provided by the median 

 nerve of the ganglion in the preceding segment. The role of the median nerve 

 was investigated by severing the one that runs from the 2nd ganghon into 

 the 3rd segment. This operation gave the same result as the removal of either 

 ganghon. Removal of the 3rd ganglion involves severing the median nerve 

 of the 2nd ganglion and it is theoretically possible that the three different 

 operations are effective because the median nerve supply is cut. This hypothesis 

 remains to be tested. A more likely explanation in my opinion is that all these 

 operations have the common effect of reducing the amount of innervation 

 and that a reduction in ,, nerve-dosage" during a period of histolosis leads 

 to the degeneration of the under-innervated muscles. This is in line with 

 findings in amphibian regeneration (Singer, 1954). 



101 



