THP: CANADIAN ENTOMOLOGIST. 71 



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BOOK NOTICE. 



The Determination of Dominance and the Modification of Be- 

 haviour IN Alternate (Mendelian) Inheritance, by conditions 

 surrounding or incident upon the Germ cells at Fertilization. By Wm. 

 L. Tower (Biol. Bulletin, Vol. XVIII, No. 6, 1910). 



Prof. Tower has been engaged in an evolutionary study of the genus 

 Leptinotarsa since 1895. In 1906* he published extensive data concern- 

 ing this group from a number of points of view. The most interesting 

 part of the results made known at that time was the production of new 

 forms by exposing the beetles to extreme conditions of temperature and 

 moisture during the period of the growth and maturation of the germ cells. 

 The new forms were bred under normal conditions, and bred true in every 

 case. All of the new forms (or nearly so) occur under natural conditions, 

 either as distinct species or as extreme variants (sports). The new forms 

 were obtained in varying proportions. In the best experiment all of the 

 progeny (those that reached the adult stage) were of the new type. 



In the present article Prof. Tower has given the results of a series of 

 experiments to determine the effect (as shown in succeeding generations) 

 of external conditions on hybridization. Here, also, extreme conditions 

 of temperature and moisture were the factors. The contrasted characters 

 in the beetles crossed were such as gave under certain conditions (normal ?) 

 typical Mendelian proportions in the second generation after crossing. 

 In crosses between Z. signaticollis and Z. diversa the results varied, 

 depending upon the conditions during mating, from one in which the 

 offspring of the first generation were all true hybrids, as shown by a 

 splitting into three groups in the second generation, to one in which ail 

 the offspring of the first and succeeding generations were entirely like the 

 female signaticollis parent. In crosses between Z. tindecimltJieata and 

 Z. signaticollis the results were similar, but more complicated, owing to 

 there being three pairs of contrasted characters instead of a single pair. 



"\V. L. Tower, Evolution in Chrysomelid Beetles of the Genus Leptinotarsa. 

 Carnegie Institution, Publication No. 48. 



