ZOOLOaT AND BOTANY, MICROSCOPY, ETC. 669 



described-— namely, suddenly killing the animal under the cover-glass, 

 and then colouring and preserving it. For Adinosplicerium a two per 

 cent, solution of chromic acid is the most satisfactory ; absolute 

 alcohol is especially to be avoided. With Amoehce, on the contrary, 

 absolute alcohol acts very satisfactorily. Wiegert's solution of picro- 

 carmine was used as a colouring reagent, and dilute alcohol, in the 

 place of water, was selected to wash the specimens. 



For some time the author was unable to observe any phenomena of 

 fission in Actinosphcerium eichJiornii, and he was almost led to believe 

 in the free development of nuclei as the only means by which these 

 structures are here formed, when he came across a small example in 

 which division was to be observed, and an explanation of the rarity 

 of the observation was to be found in the rapidity of the operation, 

 and the sharp disappearance of all the characteristics of fission. 



After describing the several stages in the Protozoon just mentioned. 

 Dr. Gruber passes to Amoeba proteus. Here, again, we have the same 

 kind of history. Specimen after specimen was examined before one 

 was seen in which the process of nuclear division could be traced : it 

 was then seen that the nucleolus first divides into two equal parts, 

 which, at first closely approximated, begin to separate from one 

 another; between them, and in the equator of the nucleus, there 

 appears a line in which is developed the new cortical layer for the 

 daughter-nuclei. The author thinks that we have here to do with a 

 low form of indirect division, this mode being, as it seems, conditioned 

 by the arrangement of the chromatic substance in the nucleus. It is 

 arranged circularly in a cortical layer, and forms a single central 

 regular mass. Direct division is occasionally, though rarely, to be 

 seen among the Protozoa, as e. g. the division by constriction of the 

 nucleus in Amceha polypodia. Mechanical difficulties may oppose 

 direct division ; thus, if it take place while the Amceha is in move- 

 ment, the whole protoplasm and the nuclei will be affected by 

 currents. 



The paper concludes with the account of some observations on an 

 undetermined species of Amoeba, in which the nucleus was seen to 

 divide into two, generally unequal, halves. We find, therefore, that 

 amoDg the Amoehce there are two kinds of nuclear division — a direct 

 one, in which the nucleus undergoes a kind of hour-glass constriction, 

 and a more indirect one, in which the nucleoli are primarily and the 

 halves of the nucleus only secondarily affected. 



Observations on Actinosphaerium eichornii.* — Miss S. G. Foulke 

 states that while observing Actinosphoeria four individuals were seen 

 to become fused, as it were, into one mass. At the end of an hour, 

 this mass had separated into three Actinosphoeria, two of the original 

 four remaining fused into one. This double one then became con- 

 stricted, a little to one side of the middle, apparently being about to 

 separate. In a few minutes the Actinosphoeria began to eject, at the 

 point of constriction, a thin protoplasmic substance containing trans- 

 parent granulated globules and free granules. By a waving motion 



* Pi-oc. Acad. Nat. Sci. Philad., 1883, pp. 125-7. 

 Ser. 2.— Vol. III. 2 Y 



