ml KEGENERATION, OR GROWTH AND REPAIR 147 



been studied by Lillie*, who found that in Stentor, while still 

 smaller fragments were capable of surviving for days, the smallest 

 portions capable of regeneration were of a size equal to a sphere of 

 about 80 jj, in diameter, that is^ to say of a volume equal to about 

 one twenty-seventh of the average entire animal. He arrives at 

 the remarkable conclusion that for this, and for all other species 

 of animals, there is a "minimal organisation mass," that is to say 

 a "minimal mass of definite size consisting of nucleus and cyto- 

 plasm within which the organisation of the species can just find 

 its latent expression." And in like manner, Boverif has shewn 

 that the fragment of a sea-urchin's egg capable of growing up into 

 a new embryo, and so discharging the complete functions of an 

 entire and uninjured ovum, reaches its limit at about one-twentieth 

 of the original egg, — other writers having found a limit at about 

 one-fourth. These magnitudes, small as they are, represent 

 objects easily visible under a low power of the microscope, and so 

 stand in a very different category to the minimal magnitudes in 

 which life itself can be manifested, and which we have discussed 

 in chapter II. 



A number of phenomena connected with the linear rate of 

 regeneration are illustrated and epitomised in the accompanying 

 diagram (Fig. 40), which I have constructed from certain data 

 given by Ellis in a paper on the relation of the amount of tail 

 regenerated to the amount removed, in Tadpoles. These data are 

 summarised in the next Table. The tadpoles were all very much 

 of a size, about 40 mm. ; the average length of tail was very near 

 to 26 mm., or 65 per cent, of the whole body-length; and in four 

 series of experiments about 10, 20, 40 and 60 per cent, of the tail 

 were severally removed. The amount regenerated in successive 

 intervals of three days is shewn in our table. By plotting the 

 actual amounts regenerated against these three-day intervals of 

 time, we may interpolate values for the time taken to regenerate 

 definite percentage amounts, 5 per cent., 10 per cent., etc. of the 



* Lillie, F. R., The smallest Parts of Stentor capable of Regeneration, 

 Journ. of Morphology, xii, p. 23.9, 1897. 



t Boveri, Entwicklungsfahigkeit kernloser Seeigeleier, etc., Arch.f. Entw. Mech. 

 II, 1895. See also Morgan, Studies of the partial larvae of Sphaerechinus, ibid. 

 1895; J. Loeb, On the Limits of Divisibility of Living Matter, Biol. Lectures, 1894, 

 etc. 



10—2 



