Regeneration in Compound Eyes of Crustacea • 235 



found to be antenna-like. That its inner structure should be 

 antenna-like might be expected since its innervation is associated 

 with a region of the central nervous system that is particularly 

 concerned with the innervation of the special sense organs, and 

 since its outward form is antenna-like it is rather to be expected 

 that the inner structure would also conform more or less to the 

 antenna type. 



It seems evident that the ganglionic groups of sense cells which 

 are found in the heteromorphic appendage, belong to the general 

 peripheral nervous system found so widely distributed among the 

 different Arthropods. The groups of cells and the associated 

 sensory hairs are equivalent to the "Hautsinnesorgane" of vom 

 Rath ('94). Ost Hoc. ctt.), however, does not regard these sense 

 cells as true ganghon cells, as Herbst does. In the regenerating 

 antenna of Oniscus, Ost finds the nerve fibers regenerating from 

 the central stump and the groups of sense cells differentiating from 

 the hypodermis. The regenerating nerve fibers come from the end 

 of the nerve stump, extend to the peripher}' and intermingle with 

 the sense cells. Bethe ('96) considers that the peripheral nervous 

 system of Arthropods differs both in function and origin from the 

 central nervous system. Holmgren ('95) regards it as a sort of 

 sympathetic svstem. 



That cutting the peripheral terminations of the optic nerve may 

 induce the regeneration of a heteromorphic appendage seems to 

 receive some support from the results obtained bv Zelenv upon the 

 blind crayfish. Although reduced in size the optic ganglion is 

 still present in the rudimentary eyes of blind crayfish. On the 

 other hand the ommatidial structures are entirelv wanting. So 

 long as the vestigial eve remains undisturbed there seems to be no 

 tendency toward the development of an antenna-like organ. But 

 when the optic ganglion is removed a heteromorphic appendage 

 appears. Such appendages are apparently functional as sense 

 organs and Zeleny concludes that in the blind crayfish a non- 

 functional organ has been replaced by a functional one. 



The suggested explanation for the outgrowth of the hetero- 

 morphic appendage also carries with it an implied explanation of 

 the non-appearance of a heteromorphic structure in place of a 



