18 Allgemeine Biologie und Entwickelungslehre. 



one grandparent as well as the "dominant" characteristics of the other. Thus 

 "extracted recessive" albino mice must contain gray "blood", because by cross- 

 ing them with black mice, some gray young are produced. The author sup- 

 poses that half the germ cells of a hybrid between a gray and a white mouse 

 bear the gray character with the white latent G(W), and the other half bear 

 the white character with gray latent (G)W. The result of mating such hybrids 

 together is represented by the formula 1 G(W) + 2 G(W) (G)W + 1 (G)W, where 

 the enclosing of a letter in parentheses indicates that the character designated 

 is present in the germ cell, though in a latent condition. It may become 

 active under suitable conditions. This principle is developed to cover all cases 

 of Mendelian inheritance. - - See Wilson I 1 ). 



Pearl shows that Chilomonas paramecium living in an unfavorable natural 

 environment is smaller in size than when living under favorable conditions. 

 The variability and correlation are little affected in this case by the character 

 of the environmental conditions. 



Pearl & D unbar present data on variation in length of body in 4500 indi- 

 viduals of Paramecium caudatum. Definite evidence is given of the reduction 

 of variability following selection of ancestry. It is shown that by rearing P. 

 in the proper culture solution it is possible to overcome completely the effect 

 of selection of ancestry on the variation. 



Clawson reports on a biometrical study of the inter-correlations between the 

 three distal joints of the cheliped and of the first two walking legs in Cam- 

 barus propinquus, with special reference to the influence of homology on cor- 

 relation. It is found that there is no markedly higher correlation between 

 serially homologous joints than between non -homologous joints. All the cor- 

 relations are very close. 



McCracken continues her studies [s. Bericht f. 1905 Arthr. p 13] on color 

 inheritance in Lina lapponica and contributes new data for inheritance in 

 Gastroidea dissimilis. In G. d. "black" is dominant and "green" is recessive, 

 whereas in L. I. "black" is recessive and "spotted brown" is incompletely 

 dominant. In each species the dominant character is that which appears first 

 in the development of the maturing adult, and the recessive color is that ap- 

 pearing last. In each species the recessive character breeds true at once, 

 while the dominant character only breeds true in the third or fourth generation 

 from the hybrid through the completely dominant line. There is a progression 

 or accumulation in the dominance from generation to generation in the par- 

 tially dominant line. The inheritance is not typically Mendelian but there is 

 "apparently an actual prepotency of the dominant character that in the long 

 run effectually eliminates or reduces the recessive character to a latent one". 



Tower publishes the results of a very extensive investigation of the method 

 of evolution in Leptinotarsa. Dealing first with the geographical distribution 

 and dispersion of the members of the genus it is shown that southern Mexico 

 is probably to be regarded as the center of origin of L. ; the dispersal of the 

 various groups from this center is discussed in detail. The facts of distri- 

 bution are held to "indicate in the strongest terms that there has been no 

 discontinuity in the evolution of the genus". Detailed data are presented 

 regarding individual, "place", and geographical variation in the following cha- 

 racters: the color pattern of the pronotum, the epicranium, the elytra, the 

 ventral surface of the body, the legs, the mature larvae; the punctation of the 

 elytra and of the prouotum ; the glands of the elytra ; and the size and shape 

 of the body. Variation in all species and characters is found to be determin- 

 ate and in few directions. Coloration shows variation in only two directions, 



