1905] CURRENT LITERATURE 309 
(1) statolith effect; (2) anti-ferment reaction; (3) the processes hindered by shock; 
(4) transmission of stimulus; (5) curvature.—C. R. B 
A NOTABLE FEATURE of the recent meetings of the affiliated scientific organi- 
zations at Philadelphia was the annual discussion before the American Society 
of Naturalists, which this year had for its subject the mutation theory. Two 
of the seven addresses were botanical, D. T. MacDovuGat opening the discussion 
from the standpoint of plant-breeding, and L. H. Barrey presenting the taxo- 
nomic bearing of the theory. In the opening address MacDoucat” stated the 
main thesis of the mutation theory thus: “the saltatory movement of characters 
Tegardless of the taxonomic value of the resultant forms,” its principal corollary 
being “‘that the saltations in question do result in the constitution of new species 
and varieties.” He believes that many current misconceptions regarding species 
are due to the failure to discriminate between elementary species and the com- 
posite or “group” species of the systematist; and that there is accumulating 
evidence that the supposed deleterious effects of close-fertilization are groundless. 
arning is given of the confusion which must arise through the unguarded use 
of the terms “mutation” and ‘‘variation” to designate phenomena of segrega- 
tion and alternative inheritance in hybrid strains. It will be recalled in this 
connection that in a previous paper MacDoucat'® has discussed the difference 
tween fluctuating and mutative variations, and has included as mutative 
Variations only “newly arisen and transmissible qualities,” emphasizing the 
fact that it is a pure presumption to designate any aberrant condition a mutation 
until its hereditary character has been demonstrated. Regarding the causes 
of mutations little is known, but the results of the mutation cultures both at 
Amsterdam and at New York are held to indicate that they arise in greater 
numbers under environmental conditions which are especially favorable for 
vegetative development and seed-production. Some mutations occur much more 
frequently than others, and the highest total number of mutants found in any 
Progeny of Onagra Lamarckiana in New York was over six per cent., as com- 
Pared with the five per cent. maximum observed by DE Vries in Amsterdam. 
“port on other mutating species is promised for the near future—G. H. SHULL. 
‘7 MacDoveat, D. T., Discontinuous variation and the origin of species. Tor- 
Teya 5:1-6. 1905, 
ie MacDoveat, D. T., Mutation in plants. Amer. Nat. 37:737-779- 1993- 
*9 Jorpan, D. S., Some experiments of Luther Burbank. Pop. Sci. Monthly 
*201-225, figs. 22, 1905. 
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