48f> Dr. A. Gruber on the 



(B) the pseudopodia disappear, altliougli a feeble flow of pro- 

 toplasm is at first still visible, and in course of time the frag- 

 ment dies completely. I divided suchan Amceha on April 14 ; 

 on the 16th the one half was as active as at first, but the 

 other had become globular and was in course of perishing : 

 when stained the former proved to be the nucleate and the 

 latter the non-nucleate half; and the same result was fur- 

 nished by all other experiments *. Here^ therefore, the re- 

 moval of the nucleus also immediately superinduces an alteration 

 of the mobility, lohich tvill not be the case in the Infusoria or 

 probably in most Protozoa, at least even in Heliozoa I have 

 seen non-nucleate fragments move as freely as the nucleated 

 ones. But lohat is superinduced in all Protista, and generally 

 in every cell, by the want of the nucleus is the incapacity to re- 

 place lost parts, to produce neio structures. 



Thus for the " maintenance of the plastic energy of a 

 cell," as Nussbaum expresses it, the nucleus is, in fact, 

 indispensable ; and we may say with Weismann t, that " only 

 under the influence of the nucleus the transformable cell- 

 substance again acquires the full specific type." By a purely 

 empirical course we are here placed before the incontrovertible 

 fact that the nucleus is the most important and the species- 

 preservative constituent of the cell, and that to it is justly 

 ascribed the highest importance in the processes of fecundation 

 and inheritance, as has been done of late by many naturalists. 



As the directing influence in the increase of cells emanates 

 from the nucleus, it appears wonderful that the nuclear sub- 

 stance is often distributed in more or less numerous fragments 

 in the protoplasm, so that, to a certain extent, instead of a 

 monarch, an oligarchy exists in the cell, which, we might 

 suppose, could easily produce a confusion in the deve- 

 lopment. Perhaps, to obviate this and also to permit a 

 uniform distribution of the nuclear substance in the daughter- 

 individuals, in most multinucleate Infusoria we observe a 

 preliminary union of the numerous nuclei into one. When 

 this amalgamation does not take place during multipli- 

 cation \ we must conceive of all the nuclei of the same 



* In his '■^Amceha villosa,'" VVallicli twice observed a spontaneous division 

 ■without participation of the nucleus, in which the two daughter-indivi- 

 duals behaved in exactly the same vv^ay as those artificially produced ; 

 whether the non-nucleate portion afterwards perished is not mentioned 

 (see Wallich, " Amoeba villosa, &c.," in Ann. & Mag. Nat. Hist. ser. 3, 

 vol. xi. p. 444.) 



t Weismann, ' Die Continuitat des Keimplasmas als Grundlage einer 

 Theorie der Vererbung,' Jena, 1885, p. 29. 



X According to Biitschli, as is weU known, the nuclei do not become 

 amalgamated during fission in Loxodes rostrum. I have also always found 

 individuals of this Infusorian which were just engaged in dividing, to be 



