FORM REGULATION IN CERIANTHUS. 313 



556. Marginal tentacles 1 1.5 mm.; in one specimen with 

 rather unequal tentacles a few 3 mm. 



January 1 1 : Twenty-seven days after section : 



54/\. Marginal tentacles 56 mm.; transverse bands of pig- 

 ment distinct; labial tentacles 1 1.5 mm. At aboral ends no 

 well-marked outgrowth of new tissue ; ends slightly lighter in 

 color at region of closure. 



546. All still collapsed, much contracted, rounded in form. 



5 5 A. Oral ends similar to 54A. At aboral ends a distinct 

 outgrowth of new tissue 23 mm. 



55 B. Marginal tentacles 35 mm.; pigmentation of tentacles 

 slightly less deep than in 54 A ; labial tentacles just visible I 

 mm. 



January 2 1 : thirty-seven days after section : 



54 A. Marginal tentacles 7-8 mm.; labial tentacles 1-1.5 

 mm. No distinct outgrowth of new tissue at aboral ends. 



546. Collapsed, rounded and still further reduced in size. 



5 5 A. Marginal tentacles 6-8 mm.; labial tentacles 1-1.5 

 mm. At aboral ends distinct outgrowth of new tissue 3-5 mm. 

 At this time the average length of the marginal tentacles in these 

 pieces is somewhat less than in 54 A. In the latter cases there 

 are fully as many specimens with tentacles 8 mm. in length as 

 with tentacles 7 mm. In 55 A, however, only a few pieces, and 

 these the largest, possess marginal tentacles 8 mm. in length ; in 

 nearly all the marginal tentacles are 67 mm. Moreover, the 

 average length of the labial tentacles in 55 A is slightly less than 

 in 54 A. These pieces are evidently falling behind the longer 

 pieces. 



556. Marginal tentacles 56 mm., somewhat less deeply 

 pigmented than in 54 A ; labial tentacles i mm. 



At this time the regenerated structures had acquired their 

 maximum size ; afterward reduction in size, which always occurs 

 in the pieces kept without food, began. For present purposes it 

 is not necessary to follow the history of these pieces further. 



Comparison of the data afforded brings to light a number of 

 interesting results. Comparing the rapidity of regeneration in the 

 different pieces, it is seen that the oral ends of pieces 54 A and 

 5 5 A, which represent approximately corresponding regions of 



