Descendenz und Hybriden. — Physiologie. 191 



for in the direction of the phenomena of Imitation. In many 

 cases a particuiar activity has to be well formulated at the start 

 to be of any use to the animal. In this respect mutation is a 

 better explanation of what is known than the idea of slow fluc- 

 tuating variations. 



Macdougal, D. T., Discontinuous Variation and the 

 OriginofSpecies. (Also published in Torreya. Vol. V. 

 p. 1—6. Jan. 1905.) 



States main thesis oi mutation theory, saltatory movements 

 of characters regardless of the taxonomic value of the resultant 

 forms. Points out that while Lamarck's Evening Primrose 

 [Oenotliera lamarckiana] affords a striking example of discon- 

 tinuous Variation and has been much and carefully studied, it is 

 not on the facts recorded for this plant alone, that the theory of 

 mutation rests. Enough recorded data for other species is found 

 to Support the theory, even in the absence of this especially 

 favorable form. Passes from this to the consideration of the 

 importance of hybridization in the study of unit-characters in 

 a segregated condition. 



Discusses the question of collective or group-species as 

 ordinarily recognized by taxonomists and points out that it is 

 highly essential to also recognise the elementary species of 

 which these consist. This is of the first importance in the 

 discussion of the physiologic or phylogenetic side of the question. 

 In the matter of the possible causes of mutations concludes 

 that in general, favorable environmental conditions, appear to 

 be favorable for the formation of new species. 



H. M. Richards (New York). 



LiviNGSTON, B. E., Chemical Stimulation of a Green 

 Alga. (Bull. Torrey Bot. Club. Vol. XXXII. p. 1—34. 

 Fig. 1 — 17. Jan. 1905.) 



The author used the same form of Stigeocloniiim for these 

 researches as he employed in his previous work on osmotic 

 pressures. A very large number of salts were used, asfollows: 

 AL' (NOs)^; AI. [^0^y.\ NHi NOs; iNHj).. SOi; Ba (NO.^-; 

 Ca(N03).'; Cd (N03)l>; Co(N03)2; CoSO^; Cu(N03)2; CuSO^; 

 HNO3; H2SO4; Fe. (N03)6; Pb (NOs).; LiNOs; Li..S04; Mg 

 (NOs).; MgS04; Ni (NOs).-; KNO3; K2SO4; Rb2S04; AgNOa; 

 NaNOs; Na2S04; Sr (N03)2; UO2 (N03)2; Zn (N03)2; ZnSO,. 

 The concentrations in which the filaments grow in a normal 

 manner, in which they became palmella like, and in which the 

 production of zoospores was accelerated, as well as the toxic 

 concentrations, were all determined and have been carefully 

 tabulated. The important results are to be summarized briefly 

 as follows : 



1. Concludes that the Stimulation is due to the cations. 



2. At high enough concentrations death is produced. 



