SCIENCE. 



[N. S. Vol. I. No. 4. 



These are the latest group of plants to ap- 

 pear geologicallj', they grow and flower in 

 the warm season added to the short arctic 

 summer by the retreat of the glacial winter. 

 The following diagram will indicate more 

 clearly what is meant, and will show why it 

 is that the Compositte of the north temperate 

 zone are the characteristic herbaceous vege- 

 tation of the late summer and autumn 

 months. 



Peesent Astronomical Yeae. 



Glacial Summer. 



Glacial Winter. 



Miocene Season of Growth. 



The land area left bare by the retreat of 

 the glaciers was one of low tension, althou^gh 

 by the increase in the length of the summer 

 (some three months) it had a climate in 

 every way suited for the growth of plants. 

 The country to the south was one of very 

 high pressure tension, which must be re- 

 lieved. The great strain was removed 

 partially by the movement of plants to the 

 northward. " Of all the plants which went 

 south before the first invasioii of the glacial 

 ice sheet, none showed greater capacitjr for 

 variation and improvement than the ances- 

 tral forms of the modern dominant familj^ 

 of Compositse." Such plants in having 

 seeds adapted to fly before the prevalent 

 north winds had reached a low latitude, 

 where great change of form took place 

 owing to the intense struggle for existence. 

 The composite plants were assisted north- 

 ward by the same structural means as 

 carried them south. Modified considerably 



into new forms bj' their migrations and 

 life in the south, they retained their fond- 

 ness for a warm climate. By the extension 

 of the arctic summer, some three months, 

 they had an ojjportunitj^ for extensive 

 migration over the country formerly ice 

 bound. 



It is thus fi-om the high and low pressures, 

 caused alternately by the glacial epoch, 

 that the distribution of our flora in time 

 has been accomplished. 



John W. Haeshberger. 



Univeesity of Pennsylvania. 



ON CERTAIN HABITS AND INSTINCTS OF 

 SOCIAL INSECTS. 



If the mere inductive evidence for the 

 Lamarckian theory of the hereditary trans- 

 mission of acquired characters be strong 

 anj^'here, it is assuredly in the region of 

 nervous and mental phenomena. Eomanes, 

 whose reserve on the inheritance of ac- 

 quired characters of a phj^sical nature is 

 everj^where manifest, admits that manj' in- 

 stincts are due to the ' lapsing of intelli- 

 gence.'* "Just as in the lifetime of the 

 individual, adjustive actions which were 

 originally intelligent may by frequent repe- 

 titions become automatic, so in the lifetime 

 of the species actions originallj- intelligent 

 maj', b}^ ft-equeut repetitions and hereditj^, 

 so write their eflects on the nervous system 

 that the latter is prepared even before indi- 

 vidual' experience to perform adjustive ac- 

 tions mechanically which in previous gen- 

 erations were performed intelligently." 



Even Weismaun, with all his wealth of 

 imagination and capacity for elaboration 

 of details, has nowhere attempted to trace 

 out the mechanism for the evolution of in- 

 stinct on the line of his ' germ plasm the- 

 orj%' nor applied to it the manifold combi- 

 nations of ' biophors ' and ' determinants,' 

 ' ids ' and ' idauts ' which he assumes as the 

 machinery of inheritance. So far the only 



*3fental Evolution in Animals, p. 178. 



