140 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



one twentieth of the body-length, have been observed to regenerate 

 completely. 



The rapidity of regeneration is greatest at the oral end and de- 

 creases aborally, until in a short aboral region complete regeneration 

 does not occur. Apparently the power of growth and in general the 

 reactive capacity of the tissues are greatest at the oral end and 

 decrease aborally. 



Rapidity and amount of regeneration are influenced by tempera- 

 ture, increasing with rise and decreasing with fall of tempera- 

 ture. This influence of temperature is clearly seen in the difference 

 in the rapidity and amount of regeneration in summer and in winter, 

 the temperature of the water being much lower during winter. 



In pieces above the minimum, size has no effect on the rapidity 

 of regeneration and only a very slight effect in the later stages upon 

 the amount. In other words, the new parts are far from being 

 proportional to the size of the piece from which they arise. A piece 

 five millimeters in length produces tentacles of about the same length 

 as a piece twenty or thirty millimeters in length. Only after several 

 weeks does the smaller piece fall slightly behind the larger. These 

 facts make it evident that porportionality is by no means retained in 

 the regenerating pieces of Cerianthus and are therefore difficult to 

 reconcile with those theories in which this proportionality plays an 

 important part. 



It was found to be possible to analyze to a certain extent the 

 process of regeneration and to inhibit it experimentally. The more 

 important results obtained from these experiments are given briefly 

 in the following paragraphs. 



As regards the growth of tissue from cut surfaces of the body- 

 wall, it was found that new tissue arising from cut surfaces appears 

 to obey the laws of capillarity to some extent. New tissue was 

 never seen to grow out from a single exposed cut surface ; the sur- 

 face may heal over, but no further growth occurs. When, however, 

 two cut surfaces are in contact, union between them occurs, and the 

 growth thus initiated may continue in the form of a thin membrane 

 with concave free margin for a certain distance between two 

 diverging cut surfaces. The distance to which the membrane is 

 capable of extending depends, in a given species of Cerianthus, on 

 the angle of divergence of the cut surfaces — the greater the angle 

 the less the distance over which the new membrane of new tissue 

 can extend. It follows that if the angle of divergence be too great 

 for the extension of this membrane, the wound cannot close. Thus, 

 by preventing contact of cut surfaces or by fixing their position at a 



