: 



in 



REGENERATION ANIMALS AND PLANTS 35 



Regeneration. Finally, experiments have been made by 

 several observers as to the effects of removing parts of Protozoa, 

 to see how far regeneration can take place. The chief results 

 are as follows : 



1. A nucleated portion may regenerate completely, if of 

 sufficient size. Consequently, multinucleate forms, such as 

 Actinosphaerium (Heliozoa, Fig. 19, p. 72), may be cut into a 

 number of fragments, and regenerate completely. In Ciliata, such 

 Stentor (Fig. 59, p. 156), each fragment must possess a portion 

 f the meganucleus, and at least one micronucleus (p. 145), and, 

 moreover, must possess a certain minimum size. A Eadiolarian 

 central-capsule " (p. 75) with its endoplasm and nucleus may 

 generate its ectoplasm, but the isolated ectoplasm being non- 

 nucleate is doomed. A " central capsule " of one species introduced 

 to the ectoplasm of another, closely allied, did well. All non- 

 ucleate pieces may exhibit characteristic movements, but appear 

 unable to digest ; and they survive only a short time. 1 



Animals " and " Plants 



Hitherto we have discussed the cell as if it were everywhere 

 an organism that takes in food into its substance, the food being 

 invariably " organic " material, formed by or for other cells ; 

 such nutrition is termed " holozoic." There are, however, limits to 

 the possibilities in this direction, as there are to the fabled 

 capacities of the Scillonians of gaining their precarious liveli- 

 hood by taking in one another's washing. For part of the food 

 material taken in in this way is applied to the supply of the 

 energies of the cell, and is consequently split up or oxidised into 

 simpler, more stable bodies, no longer fitted for food ; and of the 

 matter remaining to be utilised for building up the organism, a 

 certain proportion is always wasted in by-products. Clearly, 

 then, the supply of food under such conditions is continually 

 lessening in the universe, and we have to seek for a manufactory 

 of food-material from inorganic materials : this is to be found in 

 thuse cells that are known as " vegetal," in the widest sense of 



1 SeeGruber in Biol. Centralb. iv. p. 710, v. p. 137 (1884-6), in /At. Ges. Freiburg, 

 i. ii. 1886-7 ; Verworn (reference on p. 16) ; F. R. Lillie in Journ. Morph. xii. 1896, 

 p. 239 ; Nussbaum in Arch. miTcr. Anat. xxvi. 1886, p. 485 ; Balbiani inliecueil Zool. 

 Suisse, v. 1888, in Zool. Anz. 1891, pp. 312, 323, in Arch. Mierogr. iv. v. 1892-3. 

 For Higher Organisms especially see T. H. Morgan, Regeneration, 1901. 





