193] REGENERATION OF CRAYFISH APPENDAGES 5 



Herrick says that, although so far as known, autotomy does 

 not occur in the antennae, regeneration may take place at any 

 articulation in the flagellum or the stalk. In the young lobster 

 the flagellum of the second antennae may be completely restored 

 without an intervening moult, but in adult individuals one moult 

 at least seems necessary for complete restoration. The internal 

 changes, which do not differ from those observed in crayfish, 

 will be referred to in the discussion of the same phenomena 

 there. 



The next experimenter upon regeneration in Crustacea was 

 Herbst. As material for experiment he has used Decapods of 

 at least three different families and two genera of Isopods. 

 His experiments have included the removal of both the whole 

 and a portion of the eye, and have extended over the past five 

 or six years. The first series of experiments was confined to 

 the shrimp, Palaemon ('95), and was primarily undertaken for 

 the purpose of determining whether presence or absence of light 

 has any influence upon regeneration of the eyes. The whole of 

 one or both of the eyes was removed, in most cases only one, 

 for the removal of both eyes was attended with such excessive 

 bleeding that it usually resulted in the almost immediate death 

 of the animal. The experiments were begun in October, but 

 not until the following March was any regeneration apparent. 

 When at last the regenerated structure did appear, it was an 

 antenna-like organ, not an eye. Herbst speaks of these struc- 

 tures as "antennendhnlichen-Organen." They are not alike 

 for all individuals but exhibit two general types, the first, a short 

 horn-like process consisting of at most two segments, and the 

 second, a longer, segmented out-growth resembling the flagel- 

 lum of an antenna. On the short horn-like processes long seg- 

 mented setae or hairs were conspicuous, and these Herbst re- 

 gards as sensory (1. c, p. 5o7, Figs. 2 and 6). The long an- 



