12 



cases (h^ the developmewfe of abnormal types « In the case of 

 Zygneraa.*as described by Klebs, irregular, spirally twisted 

 structures are produced., (Compare figure 2). I found that 

 growth of the scar-membrane of Anadyomene in aquarium cultxire, 

 always leads to abnormal rhlzold-llke forms. Undoubtedly In 

 both cases the abnormal activity of the growth may, under suit- 

 able culture-conditions, be replaced by normal formative processes 



Finally those conditions are still to be discussed, the ful- 

 fillment of which must be considered as taken for granted in the 

 process^ of restitution already described. 



Eiqperiments with protozoa have proved that isolated csrfeo- 

 plasm can form no new nucleus from its own substance and that is- 

 . olated nuclei «re just as little able to form cytoplasm. The re- 

 generation of the cytoplasm presupposes a fragment of cytoplasm, 

 the regeneration of the nucleus, a fragment of the nucleus. Fur- 

 ther - regeneration of the cytoplasmic bodies from a rewnTiTft of 

 cytoplasm can takq place only when a nucleus, or a fragment of a 

 nucleus, remains Connected with it and, conversely, a nuclear 

 fragment can be restored" to c normal nucleus, only when the oy- 

 (15) toplasm, or a remnnnt of it, remains attached to this fragment. 

 Isolated nuclei without cytoplasm and cytoplasmic rcasses ?/ithout 

 nuclei are incapable of living for any length of time^* At least 

 parts of cytoplasm and nuclei must remain united, if there is 

 to bd any restitution of the cell. 



These interrelationships were first observed in protozoa, 

 whose large, easily dissectable nuclei make them favorable objects 

 for experimentation'^, but for a long time they v/ere misconstrued, 

 inasmuch as the activities of the nucleus, the "element of the 

 cell which bears the inheritable ch?iracters and qualities", wer6 

 considered as the alpha and omega of all regeneration processes, 

 and the importance of the cytoplasm completely overlooked^. 



It is evident, from what has been said above, that the wall 

 so Important for plant cells, can be regenerated also on cell 

 fragments which lack it entirely, and that further, its new form- 

 ation is produced from the cytoplasm. The fact that the cyto- 

 plasm can build a new wall only in the presence of and under the 

 Influence of the nucleus is important here. Schmitz was the first 

 to prove that isolated cytoplasmic fragments from cells of the 

 multi-nucleqted Siphonocladiaceae can remain capable of life and 

 of forming new independent cells, i. e, can provide themselves 

 with R new wall , only if the severed csrtoplasmic mass has taken 



•*• Compare Verworn, Physiol, Bedeutung des Zellkerns, 

 Pfluger^s Archiv. 1891, Bd. LI, p, 1. 



^ The^^first experiments originated v/ith ITussbaum (Ueb, spon- 

 tane und Kunstliche Teilung, Sitz,-Ber, d. liederrh, (Jes. , Bonn 

 1884, Ueb, d, Teilbarkeit der lebendigen Materie. ArcJjL. f, 

 mikr. Anat. 1886, Bd. ZXVI, p. 485) and Gruber (Ueb, kunstl. 

 Teilung bei Infusorien land II, Biol. Cbl., 1884, Bd. IV, p, 

 717 and 1885, Bd, V, p. 137, Beitr, zur Kenntnis der Phys, u, 

 Biol, der Protozoen, Ber. d, Waturforsch. Ges. Freiburg, 1886, 

 Bd. 1, 2), 



3 Compare especially Verworn, Allgem, Physiclogie, 1895, 

 p, 486 ff. Theoretical discussions, on 1;he significance ef the 

 nuolgus by Ljjeb, Warum ist die Regeneration kernloser Protop5.as- 

 mastucke unmoglich oder erschwert? Arch, f, Entw.-Mech, , 1899, 

 Bd, VIII, p. 689, 



