RELATIVE STABILITY OF LIVING MATTER 



323 



but from sheer inability to support life. Manifestly all regener- 

 ation is a struggle, and a prerequisite to its accomplishment is 

 an assured base of supplies and uninjured vital organs. 



Regeneration by transformation. 1 Regeneration in some of 

 the lower animals is accomplished through rearrangement of old 

 substance as well as through the addition of new material. 



FIG. 39. Regeneration of Stentor cut into three pieces, as at A 



B : this row shows regeneration of anterior piece. C: this row shows regeneration of middle 

 piece. D : this row shows regeneration of posterior piece. This regeneration is effected 

 first of all by rearrangement of material, each piece having been supplied with a por- 

 tion of the nucleus. After Morgan, from Gruber 



If a short piece be cut from the stem of a hydra the first step 

 in the formation of a new individual from the piece is the closing 

 of the ends and a shrinking of diameter, thus making a closed cylin- 

 der, but much smaller than the stem from which it was cut. In 

 a day or two four tentacles appear at one end, and shortly the 

 piece has assumed the characteristic form and proportions of a 

 complete hydra, after which it may increase in size. The same 

 is true of a piece of a planarian or of a Stentor (see Fig. 39). 



1 Morgan, Regeneration, pp. 



