310 ARTHUR DBNDT. 



round the mouth, formed by the lips of the ambulacral grooves, has 

 become notched into lappets all the "way round and in sections the 

 alimentary canal is seen to have become very considerably complicated 

 and folded upon itself. In sections of another specimen of this date 

 the ambulacral epithelium and canals can be traced across the disc 

 very nearly to the lip of the mouth. They present the same features 

 as in normal specimens ; thus the canals exhibit the transverse muscle 

 fibres found in ordinary specimens. The' anal cone is still very 

 small. 



Nineteen days. — Little advance is to be noted except in the further 

 growth of the anal cone, which is now fairly well developed. Sections 

 show a large body cavity in the anal cone, surrounding the terminal 

 portion of the intestine, which latter is attached to the body wall by 

 strands of connective tissue. 



Twenty-one days. — In sections of a specimen of this date a blind 

 diverticulum is visible, given off from the alimentary canal at the junc- 

 tion of the stomach with the oesophagus, as described by Ludwig in the 

 normal animal. 1 There is little to distinguish a regenerated specimen 

 of this date from a normal Antedon, excepting the smaller size of the 

 visceral mass and the want of pigment upon it. 



Comparison with other Echinoderms. — So little has as yet been 

 written on the regeneration of lost parts in the Echinodermata that it 

 is difficult to make any comparison between Antedon and other forms 

 in this respect. The most important paper as yet published on the 

 subject appears to me to be that by Professor Ernst Haeckel on Comet 

 Forms. 2 



It is a noteworthy fact that comet forms are, so far as I know, only 

 described as occurring in Asteroids [e.g. Linckia, Brisinga, Asteracan- 

 thion), none being described in Ophiuroids. Schizogony, on the other 

 hand, is known to occur in both groups (e.g. Asteracanthion and 

 Ophiactis). 



In the formation of a comet form a single arm of a star-fish, after 

 separating itself from the disc, produces, by budding at the proximal 

 end, from the wounded surface, new arms ; then a new disc appears 

 and thus the perfect condition is again attained. The mouth is at 



1 Ludwig, Morphol. Stud, an Echinoderm. 



2 " Die Kometenform der Seesterne und der Generationswechsel der Echinodermen," 

 Zeit.fur wiss. Zool, Bd. 30, Suppl. 1878, 



