RECENT ADVANCES IN SCIENCE 39 



For other recent work on the effect of light upon ger- 

 mination the reader is referred to : Lehmann, E,, " Licht- 

 keimungsfragen," Zeitschr. f. BoL, vii, 191 5, p. 560 : Khng, F. 

 (" Beitrag zur Priifung der Graserkeimung," Jonrn. /. Landw., 

 xxxiii, 1916, p. 285) ; Honing, J. A. (" De invloed van het Hcht 

 op het keimen van de zaden van verschellende varieteiten van 

 Nicotiana iabacum," Bull. Deli Proefstat, No. 7, 1916, pp. 1-14). 



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

 of Manitoba, Winnipeg, Canada. 



Protozoa. — Hegner, in " The Effects of Environmental Factors 

 upon the Heritable Characters oiArcella dentata and A. poly pora" 

 (Journ. Exp. ZooL, vol. xxxix, Nov. 1919), reared the species 

 mentioned under various unusual conditions, to see what effect 

 these would have upon certain characters in future generations. 

 By submitting them to experimental environmental surround- 

 ings, such as water containing a solution of sodium silicate or 

 ethyl alcohol, various temperatures and different degrees of 

 starvation, it was found that the offspring showed a number 

 of distinct variations in the diameter of the shell, the number, 

 size, and shape of the spines. To eliminate one source of error, 

 the initial specimens were chosen from clones of known size 

 and spine character. It was found that, when forms modified 

 by this treatment were chosen as parents and were restored to a 

 normal environment, their offspring resumed normal characters. 

 Other papers include : 



Calkins, " UrolepHs mobilis Engelm : III, Renewal of Vitality through 

 Conjugation " {ibid., Oct. 1919) ; Dawson, " An Experimental Study of an 

 Amicronucleate Oxytrichia : I, Study of the Normal Animal, with an Account 

 of Cannibalism " [ibid., Nov. 191 9) ; and CoUett, " The Toxity of Acids to 

 Ciliate Infusoria " {ibid., Nov. 19 19). 



Invertebrata. — Hargitt, in "Germ Cells of Coelenterates : 

 VI, General Considerations, Discussion, Conclusions " {Journ. 

 Morph., vol. xxxiii, Dec. 1919), has brought to an end a series of 

 papers dealing with the subject indicated at the beginning of 

 the title. The author claims that in Coelenterates the germ 

 cells are first differentiated with the approach of sexual maturity, 

 and are not segregated at an early stage of ontogeny. In the 

 Hydrozoa the germ cells ma}^ arise from either or both layers 

 of the body even in the same individual, and in certain cases 

 they have been observed to come directly from differentiated 

 body cells. In the Scyphozoa the germ cells are probably 

 entodermal in origin. It is further claimed that, in view of 

 the evidence obtained from a study of the germ cells, regenera- 

 tion, budding, etc., the theory of the continuity of the germ 

 cells cannot be regarded as applying to the Coelenterata. 



