FORM-REGULATION IN CERIANTHUS. IOI 



small portion of the oesophageal circumference, only a few ten- 

 tacles are retarded and correspondingly only a few appear on the 

 lateral disc. If the cut is not deep enough to reach the cesopha- 

 gus, but involves only the body-wall, the cut surfaces of the 

 body-wall unite within a few clays and regeneration of the termi- 

 nal disc proceeds in the typical manner. 



Turning now to the consideration of specimens with fully 

 developed normal tentacles, the effect of a lateral cut in the 

 oesophageal region is not difficult to understand if we recall the 

 reduction and atrophy of tentacles in consequence of reduced 

 internal pressure which was discussed in the preceding paper 

 (Child, '04*-), and if we bear in mind also the method of closure 

 in series 42. For comparison with series 42 the history of a 

 piece of this kind is given briefly. 



Series 10. 



September 12, 1902. --A specimen with marginal tentacles 

 about 25 mm. and labial tentacles about 8-9 mm. in length was 

 used. A lateral transverse cut extending about half way through 

 the body was made in the oesophageal region as in Series 42 

 (Fig. i) but in the present case the original disc and tentacles 

 were not removed as in Series 42. 



September /p. --Seven days after section. Closure has occur- 

 red as shown in Fig. 7 and the specimen is distended. The ten- 

 tacles on the uncut side retain their original length ; marginal 25 

 mm., labial 8 mm. ; those on the cut side are reduced- - mar- 

 ginals 15-18 mm., labials 6 mm. The portion above the lateral 

 cut in which, as in Series 42, the intermesenterial chambers are 

 completely shut off from the exterior and from the main enteric 

 cavity, is less distended than the other portions as indicated in 

 Fig. 7. In this figure only the bases of the old tentacles are 

 shown but the smaller size of those on the right is indicated. 



The cut surfaces of oesophagus and body-wall on the lower 

 (aboral) side of the cut have united as in Series 42 and now the 

 regenerating marginal tentacles are about 2 mm. in length on 

 this supplementary disc (Fig. 7). 



October j. - -Twenty-one days after section (Fig. 8). The 

 tentacles on the uncut side still retain nearly their original length 



