562 SCIENCE PROGRESS 



nucleus must be different from the nucleus in the higher forms. 

 The reduction division is found to be the first division of the 

 sporoblast in D. schneideri, and probably in other forms also. 

 In none of the so-called reduction divisions has true reduction 

 been demonstrated. Particular emphasis is laid on the fact 

 of the difference between the Protozoa and the Metazoa, and 

 it is pointed out that the practice of interpreting the Protozoa 

 in terms of the metazoan cell has led to serious error in the past. 

 " The relations between nuclear number, chromatin mass, 

 cytoplasmic mass, and shell characteristics in four species of 

 the genus Arcella " {Jour. Exp. Zool., vol. xxx, no. i, 1920) 

 have been dealt with by Hegner. The problem of the investi- 

 gation is fairly indicated by the title, and Arcella is very 

 favourable for this type of work, since cytoplasmic and nuclear 

 characteristics can be drawn easily at the same time from living 

 examples ; further, they are easy to keep, and offer certain 

 measurable characters that are not modified by growth. The 

 two chromatin masses in one specimen were found in general 

 to be nearly equal, but those from different specimens varied 

 considerably in size, and the mean quantity of chromatin in 

 specimens of one family was much greater than in those of 

 another. One line of A. dentata died out apparently because 

 of the small amount of chromatin as compared with the 

 cytoplasm. The paper finishes with a discussion on various 

 problems arising out of the work. 

 Other papers include : 



Cutler, " Protozoa Parasitic in Termites. Pt. II, Joenopsis polytricha, 

 n. gen. n. spec, with Brief Notes on two New Species, Joenopsis cephalotricha 

 and Microjoenia axostylis " {Quart. Jour. Micro. Set., vol. Ixiv, pt. 3, March 

 1920) ; Dawson, " An Experimental Study of an Amicronucleate Oxytricha. 

 II, The Formation of Double-animals, or Twins" [Jour. Exp. Zool., vol. xxx, 

 no. I, Jan. 1920) ; Hausman, " A Contribution to the Life-history of Amoeba 

 proteus Leidy " {Biol. Bull., vol. xxxviii, no. 5, May 1920) ; Huxley, 

 " Note on an Amoeba-like Parasite from Clavellina " {Quart. Jour. Micro. Sci., 

 vol. xxxvi, pt. 3, March 1920) ; Kofoid, " A Critical Review of the Nomencla- 

 ture of Human Intestinal Flagellates, Cercomonas , Chilomastix , Trichomonas, 

 Tetratrichomonas , and Giardia " {Univ. California Pub., Zool., vol. xx, no. 6, 

 June 1920) ; Kofoid and Swezy, " On the Morphology and Mitosis of Chilo- 

 mastix mesnili (Wenyon). A Common Flagellate of the Human Intestine " 

 {ibid., vol. XX, no. 5, April 1920) ; Kudo, " On the Structure of some Micro- 

 sporidian Spores" {Jour. Parasit., vol. vi, no. 4, June 1920) ; Todd, " Spiro- 

 chcBta recurrentis : a Filter Passer " {ibid., vol. vi, no. 3, March 1920) ; Tyzzer, 

 " The Flagellate Character and Reclassification of the Parasite producing 

 ' Blackhead ' in Turkeys — Histomonas, gen. nov. meleagridis , Smith " {ibid.) ; 

 Wight and Lucke, " A New Bi-flagellate Protozoon of Man " {ibid.). 



Invertebrata. — Papers include : 



Hyman, " The Axial Gradients in Hydrozoa III, Experiments on the 

 Gradient of Tubularia " {Biol. Bull,, vol. xxxviii, no. 6, June 1920). 



