ZOOLOGY AND BOTANY, M1GKOSCOPY, ETC. 549 



accumulate in Protozoa living freely is passed out by the vacuoles. This 

 view has been upheld by Degen, Burian, Ziilzer, and others. Stempell 

 has experimented with Paramecium, and has invented a mechanism to 

 illustrate the function of the vacuoles. The waste-products of the 

 metabolism accumulate in fluid form in branched canals leading to the 

 contractile vacuole. When, the vacuole empties itself to the exterior, the 

 ends of the canals expand like clubs, the fluid accumulating in areas of 

 least pressure. Fine valves consisting of protoplasmic lamellae allow the 

 fluid to pass into the vacuole until it is filled. When the pressure of 

 the contents of the vacuole exceeds that of the external water a small 

 opening is formed on a projecting papilla and a second valve occurs 

 there. To the pressure of the protoplasm and the surface-tension of 

 the vacuolar drop is due the complete emptying of the vacuole. The 

 contractile vacuoles doubtless subserve respiration and excretion, but 

 their chief function is the expulsion of the water which has entered by 

 osmosis. 



Studies on Protozoa.* — Bernard Collin describes Arcella atava sp.n. 

 which has a single nucleus instead of the usual two or more. Perhaps 

 the species is in this respect primitive. The nucleus is filled with 

 chromatin spherules of variable dimensions. There may be one large 

 one predominating greatly over the others, or two large ones. On the 

 surface of the plumose gill of Pterotrachea coronata, Collin found a new 

 ciliated Infusorian — Syrinyophora pterotrachese g. et sp. n. It has a 

 terminal or sub-terminal mouth, undifferentiated holotrichous ciliation, 

 a dorso-ventral flattening, and a flexion of the axis of symmetry to the 

 left. There is a long tubular pharynx, but there was no hint of food- 

 vacuoles or food-particles, and it may be that the mouth and pharynx 

 have only a fixative function. In the liver of Carinaria mediterranea, 

 the author found Opalinopsis carinarise sp. n. Its nucleus may have the 

 form of a twisted band or wreath, or it may be represented by a number 

 of chromatin fragments, or even by chromidial dust. In the receptaculum 

 seminis of the same Mollusc, Collin found Cryptobia carinarise sp. n., 

 with two flagella (each with a basal granule), a large blepharoplast 

 always on the convex surface apposed to the undulatory membrane 

 (sometimes fragmented and vacuolated), and a nucleus with a central 

 karyosome or several granules. 



Nutritive Conditions Determining Growth of Protista. f — H. G. 

 Thornton and Geoffrey Smith have enquired into the nutritive conditions 

 determining the growth of Euylena viridis and various soil Protista. 

 As regards Euylena, it was found that in solutions containing no organic 

 matter, it increases very slowly. By the addition of a trace of organic 

 infusion to the solution of inorganic salts, a good growth of Euylena can 

 often be obtained. The efficacy of the natural organic infusion in 

 stimulating the growth was very variable. Minute traces of amido-acids 

 added to the inorganic solution had a remarkable effect in stimulating 

 the growth of Euylena ; stronger solutions of amido-acids were less 



* Arch. Zool. Exper.,liv. (1914) Notes et Revue, No. 4, pp. 85-97 (5 figs.), 

 t Proc. Roy. Soc, Ser. B, lxxxviii. (1914) pp. 151-65 (1 pi.). 



