FORM-REGULATION IN CERIANTHUS, VIII. 



SUPPLEMENTARY PARTIAL Discs AND HETEROMORPHIC TENTACLES. 



c. M. CHILD. 



THE REGENERATION OF SUPPLEMENTARY PARTIAL Discs AND 



CORRELATED REGULATION. 



The regeneration of supplementary partial discs and tentacles 

 in Ceriantlms from the lateral body- wall was first described by 

 Loeb('9i). The method of procedure employed in order to 

 produce results of this kind was partial transverse section of the 

 body- wall at one or more levels. According to Loeb it is neces- 

 sary to delay the healing of the wound for a few days in order 

 to bring about tentacle regeneration in connection with it. The 

 regeneration of tentacles and disc always occurs in connection 

 with the lower (aboral) side of the wound. The number of ten- 

 tacles borne by the supplementary disc is a fraction of the whole 

 number characteristic of the complete disc and varies with the 

 portion of the circumference involved in the cut. When the cut 

 occurs near the oral end of the body the supplementary disc 

 possesses a mouth, but discs regenerated at a lower level, /. <?., 

 further aborally, possess no'mouth. 



Loeb regarded these experiments as affording an important 

 indication of the relation of growth to turgor of the cells. 

 After a transverse cut is made in one side of the body-wall the 

 tentacles oral to this region "lose their turgor" while the other 

 tentacles retain theirs. This fact, as Loeb believes, indicates that 

 the distension or erection of the tentacles cannot be due to water 

 under pressure in the enteric cavity since if that were the case 

 an opening into the enteron would cause the collapse of all ten- 

 tacles, and he concludes that the cut has in some way reduced 

 the turgor of the cells, comparing the effect with the withering 

 of plant tissues after the stem is cut. No suggestion as to the 

 manner in which the cut effects loss of turgor in the cells of the 

 tentacles is given. Certainly the case is not comparable with 



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