ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
353 
in the endoplasm or in special vacuoles of ciliated Infusorians and some 
other Protozoa. His researches relate chiefly to Paramsecium. The 
bodies consist for the most part of calcium and phosphoric acid, perhaps 
along with some organic substance in combination with calcium phos- 
phate. It seems likely that they are dissolved in plasmic fluids and 
excreted through the contractile vacuoles. 
Food-vacuoles of Infusoria.* — Miss M. Greenwood discusses the 
constitution and mode of formation of food-vacuoles in Infusoria, as 
illustrated by the history of the processes of digestion in Carchesium 
polypinum. As a result of feeding experiments she finds that the solid 
particles become gathered to a cluster with a rapid centripetal move- 
ment ; those which are more peripheral leave the boundaries of the 
vacuole, and a composite solid mass lies in clear fluid surroundings. 
This process she calls aggregation, and proceeds to consider by what 
force it has been effected. The most probable explanation is that the 
solid particles which undergo change of position in aggregation are 
dragged together by the comparatively rapid retraction of some sub- 
stance contained in the vacuole; this substance is probably viscous. 
The aggregated spherical ingesta join through the endoplasm of Car- 
chesium for a variable time. Solution appears to be capricious, so far 
that all nutrient ingesta present are not of necessity digested syn- 
chronously. When it does set in, however, certain features of the 
process are invariable ; it is effected in a fluid medium, but is rarely 
complete ; innutritious remains travel with varying rapidity towards the 
anal ridge, whence they are discharged. Other things being equal the 
intracellular sojourn of ingesta tends to vary directly with their digesti- 
bility ; masses of carmine or Indian ink are got rid of comparatively 
soon. It is suggested that the process of aggregation will be found to 
be “ an expression of obscure histological change bound up with the 
digestion of food, or more nearly with its preparation for digestion.” 
Reproduction of Foraminifera.t — Herr F. Schaudinn, from the 
study of reproduction in a large number of Foraminifera, comes to the 
conclusion that it is effected by division of the protoplasm into a number 
of pieces which secrete the test, and grow up in the way that is charac- 
teristic of the proper species. To this general statement some modifi- 
cations must be made. 
(1) The division of the protoplasm, the form taken by the parts, and 
the secretion of the test are effected within the maternal test. The embryos 
leave this test by the mouth (Ammodiscus) or, if that is too narrow, by 
breaking down the test ( Discorhina ). 
(2) The division of the protoplasm is effected within the test, but the 
shaping of the form and the secretion of the new one are effected outside 
it ; that is, the parts leave the maternal test as naked plasmodia ( Calci - 
tuba). 
(3) Division, shaping, and test-formation are all effected outside the 
maternal test ; that is, after the protoplasm of the mother has left its test 
as a connected mass ( Miliolina ). 
Before reproduction the mother-animal is always multinuclear, the 
* Proa Eoy. Soc. Lond., liv. (1894) pp. 466-72. 
f Biol. Centralbl., xiv. (1894) pp. 161-6. 
2 B 
1894 
