ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 467 



meaning only when we recognize that in these unicellular beings 

 there is no " individual " in the same sense as in the higher organisms. 

 Indeed, our abstract concepts — such as " generation," " mother," 

 " daughter " — are artificial, and do not correspond to anything in 

 nature. 



2. The idea of a " senescence " of unicellular animals is not 

 tenable. Physiologically speaking, there is a profound difference 

 between the uni- and multicellular organisms in the fact that the 

 latter only wear themselves out by living, and proceed to a natural 

 death. The unicellular animals are never so modified by the trans- 

 formation of matter that life becomes impossible. They have no 

 physiological death ; their bodies are immortal, 



y. Conjugation in unicellular and fertilization in multicellular 

 organisms are analogous processes. 



4. The body of unicellular organisms corresponds to the ger- 

 minal cells of the Metazoa, and sexual reproduction of the latter 

 may, with certain limitations, be regarded as an alternation of gene- 

 rations. We have first a generation of unicellular organisms — the 

 germinal cells — and next a generation of metazoic individuals, which 

 give rise asexually to a generation of unicellular bodies. We have, 

 in fact, an infinite series of unicellular generations side by side with 

 individuals of a higher order, which alone have a physiological end — 

 a natural death. The unicellular generations — germinal cells — are 

 potentially as immortal as the Protozoa. 



Multinucleated Protozoa.* — Dr. A. Gruber commences by re- 

 ferring to the now well-known fact that of closely allied species of the 

 same genus of Protozoa some may be uni- and others multi-nuclear. 

 Opalina is very remarkable for the large number of nuclei that are 

 found in one cell. Maupas has lately described a new form, Holo- 

 pJirya ohlonga, in which there are a niunber of nuclei ; Lagynus 

 elongatus is another holotrichous infusorian in which sometimes eight 

 or ten, and in other cases nearly a hundred nuclei are to be observed. 

 Among the hypotrichous forms we find Holofricha lacazei, H. rniilti- 

 nucleata, and Urolejptus roscovianus ; here, too, the nuclei are small, 

 spherical, and regularly distributed through the body. Nucleoli are 

 sometimes, but not always, present. Gruber, like Maupas, has 

 observed similar phenomena. 



The greatest interest about these forms is the relation of the nuclei 

 to the processes of division and conjugation ; Maupas thinks that, in 

 division, the nuclei are unaffected, and Biitschli says the same of 

 Loxodes rostrum; in Holotricha scutellum, however, Gruber observed 

 that, before division, there was fusion of the nuclei, and, as the 

 process is temporary and short, he thinks it probable that there is an 

 error of observation on the part of previous observers. 



As has been already reported in this Journal, j Gruber has observed 

 more than one nucleus in various species of Amcebce, and it is quite 



* Biol. Cenfralbl.. iv. (1885) pp. 710-7. 



t Ante. p. 260. 



2 H 2 



