FORM-REGULATION IX CERIANTHUS. 95 



Supplementary Discs in tJie CEsophageal Region. 



The method employed in producing partial supplementary 

 discs in the cesophageal region was as follows : a transverse cut 

 was made in one sideof the body-wall near the middle of the 

 cesophageal region (Fig. i), thus interrupting on one side of 

 the body the continuity of both oesophagus and body-wall, 

 while on the opposite side both remained intact. Loeb removed 

 small pieces of the body-wall near the middle of the oesophageal 

 region in his experiments of this kind, thus preventing rapid heal- 

 ingof the cut edges (Loeb, '91, text fig. i). I found, however, that 

 this was not necessary in the cesophageal region, the mere trans- 

 verse slit being in most cases sufficient to bring about the desired 

 results. Neither was it necessary to delay or prevent the union 

 of the margins of the body-wall by artificial means such as the 

 wire netting employed by Loeb for this purpose. 1 



In my experiments the pieces were usually left undisturbed 

 after the operation, though occasionally it was necessary to cut 

 a piece a second time in order to cause the production of a sup- 

 plementary disc. Loeb ('91, p. 56) himself noted that the cut 

 showed a much stronger tendency to remain open when situated 

 near the oral end, but apparently was unaware that this was due 

 to the presence of the oesophagus. 



The history of tentacle regeneration in a piece of this kind is 

 given as an example. 



Scries j.2. 



October 2j_, 1902. A large specimen (C. solitarins) of normal 

 appearance was subjected to the operation indicated in Fig. i. 

 First disc and tentacles were removed by a transverse cut just 

 aboral to the disc. Then a transverse cut extending- about half 



o 



way through both body and oesophagus was made near the 

 middle of the cesophageal region. After section the piece col- 

 lapsed, as in all cases where the enteron is opened, and became 

 distended only when closure of the enteron occurred, either by 

 union of cut surfaces or by approximation. 



1 The meshes of this netting were somewhat smaller than the diameter of the body 

 and the animals, being laid upon the netting, pushed their bodies through it, aboral 

 ends first, until the level of the partial transverse cut was reached. The wires being 

 forced into the cut prevented further movement and also, according to Loeb, delayed 

 union of the two cut surfaces. 



