Mr. J. E. S. Moore — Observations upon Amoeba. 149 



mimicry of which has been described by M. de Varigny in 

 the ' Revue Scientifique ' * ; it appears to me that this is 

 probably the case, as also in Portamnus variegatus, which 

 disappears almost completely upon coarse granitic sand, as I 

 have myself been able to observe. Be that as it may, we see 

 from these examples that concealment by isochroniatic adap- 

 tation seems to be a very widely spread fact in the different 

 orders of Crustacea, and that albinism in these animals 

 appears to be only a particular case of a very much more 

 general phenomenon of chromatic adaptation to the medium. 



XVIII. — Observations upon Amoeba, with especial reference to 

 the existence of an apparent Micro-nucleus in that Organism. 

 (Preliminary Communication.) By John E. S. Moorr, 

 A.R.C.S. (from the Huxley Research Laboratory, R. Coll. 

 Sci. Lond.). 



[Plate XII.] 



Through the laborious investigations of Maupas, Biitschli, 

 Hertwig, and others we are to-day pretty well acquainted with 

 the minute structural peculiarities and life-history of the 

 ciliate Protozoa. Regarded in the light of single cells these 

 little beings present points of structure at once both strikingly 

 different and similar to those apparent in the cells that build 

 up the Metazoan tissues. 



The karyokinetic division of the micro-nucleus (" Neben- 

 kern," ^' eudoplastule," " nucleolus ") in the ciliate Infusoria 

 is undoubtedly strictly comparable, step by step, with the 

 similar process apparent in the cells of higher forms ; but the 

 coexistence of this structure itself with the macro-nucleus, 

 which divides akinetically, is something totally unlike those 

 conditions which ordinarily present themselves in Metazoan 

 cells. 



Our knowledge of the multitude of structures included under 

 the somewhat comprehensive title of " Nebenkern " in the 

 Metazoa is still in a sufficiently unedifying condition to render 

 it impossible to say whether tliose remarkable bodies met with 

 in the gland-cells of many animals, i. e. in the cells actively 

 secreting, are normal or parasitic, or whether in such cells we 

 may not have to deal with a third structure besides the 



* de Varigny, ' Revue Scientifique,' 3' serie, t. x. p. 92, 2' sem., 1885. 



