414 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



regeneration. Each of the stumps was surmounted by a small digitiform process, 

 white in color. 



On August 14 he reexamined the carmine Antedon and found that a digiti- 

 form process 1 mm. long had already formed, resembling those of the vermilion 

 Antedon. 



The next day he examined carefully the regenerated arms of the latter. At 

 the base of each of the digitiform processes a pair of long pinnules had already 

 formed, and beyond them were numerous young pinnules in various stages. 



Perrier believes that 8 or 10 weeks should suffice for the complete regeneration 

 of an arm. 



POSSIBLE EXTENT OF HEOENERATION. 



As a result of his studies at Naples Przibram found that Antedon mediter- 

 ranea (a) is able to regenerate an excised fifth, comprising an arm pair, the corre- 

 sponding part of the disk, and parts of the centrodorsal and cirri; (&) entirely 

 halved examples can regenerate the lacking two arm pairs and single arm; (c) a 

 fifth of an animal can regenerate at least an arm pair (during which process the 

 cirri fall off) ; (d) before these operations the disk can be removed without hinder- 

 ing the regeneration, and will itself always regenerate (whether after regeneration 

 the anal tube occupies the same interradius as before has not been determined) ; 

 (e) after the removal of the disk the floor of the calyx may be completely scraped 

 without hindering the regeneration of the disk; (/) if all the arm pairs are cut 

 away close to the base these, together with the disk which is cast off after the am- 

 putation of the two arm pairs, will immediately regenerate; (g) if all the arm 

 pairs are cut away in such a way that only the centrodorsal and the cirri are left, 

 these die without regenerating; (k) on the contrary, an arm pair can regenerate 

 at least another rudimentary arm pair, though it is questionable whether or not a 

 small piece of the calyx is necessary; (i) single arms regenerate nothing; (j) 

 single pieces of the calyx regenerate nothing; (&) if the cirri are all cut away they 

 will not regenerate, at least in the time in which the other regenerations are com- 

 pleted; (I) if the cirri together with the distal part of the centrodorsal are cut 

 away the open wound heals over, but no regeneration occurs, at least in the time 

 in which the other regenerations are completed; (TO) if the disk is lost it at once 

 regenerates ; (n) if the centrodorsal with the cirri be removed and the central ner- 

 vous system be entirely destroyed the animal in a short time dies, even though the 

 parts remaining if separated possess the power of regeneration to a greater or 

 lesser degree; (o) if after the removal of the disk the central nervous system is 

 destroyed the animal dies. 



Przibram notes that the negative results are perhaps subject to future correction, 

 especially since they are based upon relatively few experiments. 



It is interesting that the destruction of the central nervous system causes death 

 if the animal be left entire, while separated parts remain alive and will to a greater 

 or lesser degree regenerate. 



Detached disks or portions of disks will not regenerate, though they remain 

 alive for several days. 



