102 



C. M. CHILD. 



marginal 2022 mm., labial 7-8 mm. The tentacles oral to 

 the lateral cut are now greatly reduced- - marginal 34 mm., 

 labial 1-2 mm. --and the tips are shrivelled; the whole region 

 above the lateral cut is greatly shrunken and wrinkled, containing 

 almost no water (Fig. 8). 



Aboral to the cut the supplementary tentacles have regenerated 

 in the typical manner- -marginals 10 mm., labials 3-4 mm. 

 The new supplementary disc on the right, and the left half of the 

 old disc now lie at nearly the same level. 



A few days later the shrivelled strip bearing the reduced ten- 

 tacles was ruptured and a part dropped off. The remaining por- 

 tions underwent complete resorption within a few days, and a disc 

 of typical form resulted. One half of this disc represented what 

 remained of the old disc and its tentacles were the tentacles of 



FIG. 7. 



FIG. 8. 



the original specimen ; the other half was the regenerated sup- 

 plementary disc. The tentacles on the old portion were still 

 considerably longer than on the regenerated portion, but a 

 gradual equalization in length occurred as might be expected 

 since conditions of internal pressure are similar about the whole 

 circumference. 



The history of other similar specimens is similar in all essential 

 respects to that described, though the number of tentacles which 

 undergo atrophy vary according to the size of the lateral cut. It 

 is possible to modify these experiments in many ways but in 

 every case that part which has no communication with the main 

 enteric cavity or the exterior and so does not remain distended 

 undergoes atrophy, while those regions in which internal pres- 



