FORM-REGULATION IN CERIANTHUS. I I I 



tended examination to show the incorrectness of this conclusion. 

 These lateral discs are no more wholly ectodermal than the 

 terminal discs of normal animals (see the figures of this paper). 



HETEROMORPHIC TENTACLES. 



Experiments. 



In two cases among the hundreds of pieces examined the 

 appearance of tentacles on the aboral end of a piece has been 

 observed. Both cases occurred in a single series and were 

 apparently due to closure of the pieces in a peculiar manner. 

 Although numerous attempts to obtain additional cases were 

 made, none were successful, the pieces failing to close in the 

 proper manner. I have little doubt that whenever closure takes 

 place in a certain manner to be described heteromorphic tentacles 

 will be formed. 



The pieces which afforded this peculiar result belonged to a 

 series intended for the study of the possible methods of closure. 

 The pieces were prepared as follows. A piece was cut oral to 

 the middle of a specimen by two transverse cuts as indicated in 

 Fig. 1 6. The oral end of the piece was in all cases just below 

 the disc in the oesophageal region, the aboral end a considerable 

 distance aboral to the aboral end of the oesophagus. The cylin- 

 drical piece thus obtained was divided longitudinally into halves 

 as indicated by the small diagram to the right of Fig. 16. Each 

 piece then represented half of the circumference of the body and 

 oesophagus. The body-wall of the piece was bounded on all 

 sides by cut surfaces, two transverse at the ends and two longi- 

 tudinal at the sides. The portion of the oesophagus in the piece 

 was bounded orally and laterally by cut surfaces, but aborally it 

 terminated in the normal manner. 



Pieces of this kind close in various ways. Some roll up 

 longitudinally and form almost perfectly typical animals, others 

 roll in part longitudinally and in part transversely and the cut 

 surfaces of oesophagus and body-wall unite according to chance, 

 i. e., union of the adjacent cut surfaces occurs, whatever these 

 may be. Many bizarre forms are produced, but they afford 

 nothing new in principle. One important fact is shown by 



