ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 767 



implied by the mollusc's peculiar method of growth. In two cases out of 

 three, however, the sponge appears to be modified to some extent by its 

 association. " It is probable that the masses, with which this paper 

 deals, will be of considerable interest to the geologists of some future 

 epoch, when the bottom of the Bay of Bengal has become dry land, if there 



be geologists then 



Protozoa 



Protozoa of the Soil.*— T. Goodey reports about thirty Protozoa 

 which he has been able to identify in cultures of soil. Of these eighteen 

 are Ciliata, such as species of Colpoda, Balantiophorw, Plearotricha, and 

 Vortkella. It is shown, however, that these exist in the soil in an 

 encysted, not in an active condition. Therefore they cannot function as 

 a factor limiting bacterial activity in the soil. But the experiments 

 on which this conclusion is based were confined to Ciliata. The Amoebae 

 and Flagellates were not dealt with. 



Studies on Amoebse.t— Maynard N. Metcalf discusses in the first 

 place the localization of the contractile vacuole. More than one portion, 

 probably any portion, of the outer layer of the endosarc may form a con- 

 tractile vacuole. When it is formed it soon associates itself with a mass 

 of granules — " just the beginning of specialization of cytomicrosomes in 

 connexion with excretion." No portion of the protoplasm will ordinarily, 

 if ever, form a new contractile vacuole so long as the already collected 

 mass of granules associated with the old vacuole persists. 



The author describes a new species of Amoeba {A. current) parasitic 

 in the rectum of tadpoles, which is marked by very rapid locomotion. 

 In connexion with the life-cycle of a Baltimore Amceba, which may be 

 A. proteus,, the author describes the formation of biflagellate spores of 

 a Cercomonad-like type. There is a fragmentation of the nucleus in the 

 parent Amoeba. He also refers to an Amceba he found at Wurzburg, 

 which produced amoebospores with fine reticulate pseudopodia. 



Effect of Excretion-products on Rate of Reproduction in Para- 

 mecium.:!: — Lorande Loss "Woodruff has begun an investigation of the 

 complex factors at work in a " hay infusion " or the like, such as 

 those which determine the interdependence of the organisms, their 

 sequence, time of appearance and disappearance. He has tested the 

 effect of different volumes of culture medium on the rate of reproduction 

 of Paramecium ; the effect of changing the culture medium daily and 

 every second day on the rate of reproduction of Paramecium ; and the 

 effect of culture medium, in which large numbers of Paramecium have 

 been living, on the rate of reproduction of Paramecium. 



He has come to the following conclusions. 1. The rate of reproduc- 

 tion of P. aurelia and P. cawiatum is influenced by the volume of the 

 culture medium, within the limits tested, and the greater the volume the 

 more rapid is the rate of division. 2. There is evidence that Para- 



* Proc. Roy. Soc, Series B, lxxxiv. (1911) pp. 165-80 (1 pi.). 

 t Journ. Exp. Zool., ix. (1910) pp. 301-31 (45 figs.). 

 X Journ. Exp. Zool., x. (1911) pp. 557-81 (11 figs.). 



:) D 2 



