RECENT ADVANCES IN SCIENCE 231 



single salts, the solutions never became markedly acid or alka- 

 line, and in the case of potassium chloride, where analyses were 

 made, it was found that the two ions were absorbed in equiva- 

 lent amounts. 



ZOOLOGY. By Prof. Chas. H. O'Donoghue, D.Sc, F.Z.S., University 

 of Manitoba, Winnipeg, Canada. 



Protozoa. — Calkins, in a paper " Uropeltis mobilis, Engelm I, 

 History of the Nuclei during Division and Conjugation " (Journ. 

 Exp. Zool., vol. xxvii, Jan. 191 9), has described the nuclear 

 changes in this rare hypotrichous ciliate. The resting macro- 

 nucleus consists of eight parts, which unite and divide three 

 times before and once after cell division. The micronuclei 

 vary in number from four to six, all but two are absorbed 

 before division ; these undergo two or three mitotic divisions, 

 and then a variable number of them are absorbed. The 

 macronuclei play no part in conjugation. The micronuclei 

 undergo maturation divisions with a reduction of the 

 chromosomes from eight to four. As many as eight pronuclei 

 may be formed, but only two are functional, the others being 

 absorbed. The migratory nucleus has an attraction sphere. 

 Five days are required for the reorganisation of the cell after 

 conjugation. Mast has investigated " Reversion in Orientation 

 to Light in the Colonial Forms, Volvox globator and Pandorina 

 morum " (ibid., Jan. 1919), and suggests that the sense of 

 orientation is dependent upon physiological conditions of the 

 colony as well as the conditions of the culture medium; it is 

 also dependent on the age of the colony. Reversion in colonies 

 exposed to constant illumination is not influenced by photo- 

 synthesis, but is probably due to changes in permeability. 

 Other papers include : 



Boyd, " Observations upon Trichomonas intestinalis in Vitro," {Journ. Parasit., 

 vol. v, March 191 9 ; Chambers, " The Effect of Some Food Hormones and 

 Glandular Products on the Rate of Division of Paramcecium caudatum {Biol. 

 Bull., vol. xxxvi, Feb. 1919) ; Flather, " The Effects of a Diet of Polished 

 Rice upon the Metabolic Activities of Param&cium {ibid., Jan. 1919) ; Juday, "A 

 Fresh-water Anaerobic Ciliate" {ibid., Feb. 1919) ; and Mason, "A Case of 

 Balantidium coli Dysentery " {Journ. Parasite vol v, March 1919). 



Invertebrata. — Papers include : 



Child, " Demonstration of the Axial Gradients by Means of Potassium Per- 

 manganate" {Biol. Bull., vol. xxxvi, Feb. 1919) ; Child and Manning, "Axial 

 Gradients in the Hydrozoa" {ibid., March 1919); and Parker, "The Organisation 

 of Renilla" {Journ. Exp. Zool., vol. xxvii, Feb. 1919). 



