288 C. M. CHILD. 



2. Cylindrical pieces usually undergo a greater or less change 

 of form durincr or after regeneration : this consists of an in- 



o o 



crease in length and a decrease in transverse diameter. 



fj 



3. The change is slight during the earlier stages of regenera- 

 tion before the oral structures are developed. It seems probable 

 that it is the result, either directly mechanical or reactive or both 

 of longitudinal tension upon the tissues. The tension in turn 

 may be due in part to internal circulatory currents and in part to 

 the habit of creeping over surfaces in the direction of the longi- 

 tudinal axis. 



4. In pieces maintained in the collapsed condition the change 

 of form is the reverse, /. e., the length decreases and the trans- 

 verse diameter increases, at least relatively. 



5. It is possible to produce forms with duplicated oral or 

 aboral ends by partial longitudinal splitting : In cases of oral 

 duplication each disc is essentially a "half" structure or frac- 

 tional structure, bearing approximately the number of tentacles 

 corresponding to the portion of the circumference which it rep- 

 resents. At the aboral end a new aboral pore may be formed in 

 case the cut does not pass through the old pore. 



6. No marked regulation, reduction or absorption of these 

 duplicated structures has been observed except occasionally in 

 cases where the duplication included only the extreme terminal 

 portions. 



7. The results of attempts to produce duplications and abnor- 

 mal forms depend largely upon chance. Whatever portions of 

 the cut surfaces come into contact unite and many peculiar forms 

 result which may be more or less modified in some cases by the 

 tensions and pressures to which the tissues are subjected. 



HULL ZOOLOGICAL LABORATORY, UNIVERSITY OF CHICAGO, 

 December, 1903. 



