ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 749 



hollowed by vacuoles, but we see distinct, rounded, floating vesicles, 

 with a dense wall and a contained liquid. 



As the animal grows the number of vesicles increases at the expense 

 of the ectoplastic vacuoles, and they end by constituting by far the 

 greater part of the mass of the body, while the importance of the ecto- 

 plasm gradually diminishes. There may, indeed, be at last merely a 

 more or less thick sheath formed by the ectoplasm. The vesicular 

 elements do not only increase by the transformation of the primitive 

 areolae of the protoplasm, for they are often found elongated or con- 

 stricted in the middle, as though they were about to divide. The degree 

 of disappearance of the ectoplasm varies much in different creatures. In 

 some the whole of the body is transformed, and, when there is no inter- 

 vesicular liquid, the protoplasm is completely formed by a reticulation 

 with polygonal alveoli ; in this case all ectoplasm disappears. In other 

 cases only a few vesicles are produced, the liquid is abundant, and the 

 ectoplasm is more or less distinct. The author denies the existence of 

 the plexus which has been described as being present in the ectoplasm 

 of ciliated Infusoria, and regards it as an optical illusion. 



Physiology of Nutrition in Protozoa.* — Dr. M. Meissner finds that 

 in the Ehizopods which he examined no chemical or optical change 

 could be detected in starch-grains or oil-drops, but that in many cases a 

 digestion of vegetable and animal albumen was observed. Many Infu- 

 soria, if deprived of other food, convert the starch they take up into a 

 substance (? dextrin) which stains red when treated with iodine solution, 

 and, later on, becomes dissolved in the body. Oil, however, remains 

 unchanged. Vegetable and animal albumens are easily dissolved by 

 Infusoria, while albumen that has been cooked appears to undergo no 

 change. 



The author remarks that in most text-books Amcehse are described 

 as " flowing around " their food ; Duncan, Leidy, and Greenwood have 

 described them as drawing in foreign particles with their hinder im- 

 mobile parts. He has himself observed both kinds of ingestion, and the 

 latter, which is not easy to make out, in Amoeba princeps. The animal 

 drew in its prey, which was in this particular case a Bacterium, by means 

 of its hinder fringe-like protoplasmic processes, while the water taken in 

 at the same time formed the ingestion-vacu le. In the anterior part of 

 the Amoeba, in which the nucleus was visible, there was no movement 

 forwards of the protoplasm, but a very lively Brownian movement, 

 during this process. 



The Ehizopoda used for observation were Amoeba princeps, A. radiosa, 

 Pelomyxa palustris, and Actinophrys sol. The Infusoria were Climaco- 

 stomum virens, Vorticella nebulifera, and Peranema trichopTiorum. The 

 first-named infusorian digested a Difflugia in about twenty-five minutes, 

 when the completely unaltered test was found in a vacuole. The un- 

 altered chlorophyll was generally excreted by the Infusoria, and the 

 chitinous carapace of a Eotifer, which had served as food for a Stentor, 

 was also seen to be extruded. 



Nature of Contractile Vacuole-t— Dr. 0. de Bruyne is of opinion 

 that the contractile vacuole of Protozoa has no communication with the 

 exterior. He does not regard it as an excretory organ, but thinks it 



* Zeitschr. f. Wiss. Zool., xlvi. (1888) pp. 498-516 d pi.), 

 t Bull. Acad. R. Sci. Belg., Ivi (1888) pp. 718-44 (1 pi.). 



