vol. ij Torrey—Mery. — Regeneration in Sagartia Davit 



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nothing definite as to the order of their appearance. The first 

 pair, second pair, or .-ill of these first six mesenteries, and indeed 

 of the first eight or ten mesenteries, may reach the oesophagus. 

 There is no fixed order of increase in size. 



The first tentacle appears between the first two mesenteries. 

 Two tentacles follow simultaneously, one on each side of the group 

 of the first four. Then four tentacles appear, not always simulta- 

 neously, however, one on each side of each of the last two. 

 Beyond this point the regeneration of tentacles was not followed. 



We have been unable as yet to ascertain definitely whether 

 the process of regeneration results in bringing the polyp hack to 

 its original condition as regards number and arrangement of 

 mesenteries and tentacles; or, to state the question in a different 

 form, whether the number and arrangement of new tentacles and 

 mesenteries are in any way conditioned by the number of ole 

 tentacles and mesenteries at the beginning of the regeneration. 

 These problems will admit of ready solution as soon as a further 

 supply of material is obtained. It may be definitely said, how- 

 ever, that regeneration does not tend to restore a particular 

 structural type. The sexual type, at present unknown, is prob- 

 ably itself variable. A small percentage of regular hexamerous 

 diglyphic polyps is found. If this be assumed as the sexual 

 type, which will then be the fundamental type of the species, in 

 all probability, it is clear that such regeneration as shown in 

 Figs. 5 and (i does not tend to establish it. Many polyps are 



Figs. 5 and 6. Semi-diagrammatic cross sections of polyps 

 in process of regeneration, showing perfect mesenteries and 

 zone of regeneration (X). 



