March 27, 1908] 



SCIENCE 



493 



other shells, dead or alive. (4) Another 

 mollusk of this genus, Litorina rudis, dis- 

 plays nearly all of the color variations to 

 be found in palliata, yet rudis lives on the 

 bare rocks, and is very seldom found upon 

 the weed. (5) Experiments (still incom- 

 plete), in which the mollusks were exposed 

 to the attacks of the tautog, point to the 

 conclusion that this tish is nearly or quite 

 as likely to pick out one of the mollusks 

 from a background of a harmonious color 

 as from one which is not in the least har- 



Some Experiments in Heredity in Mice: 

 T. H. Morgan, Columbia University. 

 A wild "sport" of the house mouse, hav- 

 ing a pure white belly, slightly yellowish 

 flanks, and gray dorsal surface, was crossed 

 with the principal types of domesticated 

 breeds (black, chocolate, white) having uni- 

 form or self-colored coat. The white belly 

 dominates in the first generation, although 

 the spotted coat of domesticated races is 

 recessive to the imiform coat. Thus the 

 same character, viz., spotted coat, is dom- 

 inant in one form and recessive in the 

 other. When the sport with white belly is 

 crossed with domesticated spotted mice the 

 white-bellied character dominates. Crosses 

 between the sport and yellow mice give 

 some yeUows. These are whitish below, 

 but appear to show no more white than do 

 ordinary yellows, so that it is not possible 

 to ascribe the result to the dominance of 

 the sport. The absence of a sharp line in 

 the yellow hybrids between the yellow and 

 white would seem rather to indicate that 

 the yellow coat as a whole dominates the 

 spotted coat of the sport, which seems para- 

 doxical in the light of the relation of the 

 spotted coat of the sport to the uniform 

 coat of other colors. Cuenot's important 

 experiments with yellow mice have shown 

 that mice of this color always throw mice 

 of other colors in definite proportions. He 



accounts for the result on the basis of se- 

 lective fertilization— a yellow-bearing germ 

 cell never fertilizing another yellow-bear- 

 ing germ cell, but always one bearing an- 

 other color. The following result shows 

 that the peculiar behavior of the yellow 

 color in inheritance is not due to selective 

 fertilization, but to a different condition. 

 A yellow mouse crossed with a black-and- 

 white waltzer of pure strain, produced 

 some yellows. A pair of these yellows in- 

 bred gave yellow, black, chocolate and 

 albino mice. The result shows on analysis 

 that the yellow germ cells must carry other 

 colors, as well as yellow, and that these 

 colors reappear in the next generation. 



The Limb Muscles of Necturus, and their 

 Bearing upon the Question of Limb 

 Homology: H. H. Wilder, Smith Col- 

 lege. 



The bones and muscles of the distal half 

 of both fore and hind limbs in Necturus 

 were reviewed by means of charts and 

 drawings. These show a remarkable de- 

 gree of correspondence, extending often to 

 minor details, but there is no such corre- 

 spondence in the proximal portion (proxi- 

 mal to elbow and knee). 



This almost perfect correspondence in 

 the case of what is perhaps the most primi- 

 tive land vertebrate is of far more signifi- 

 cance than if we had found it in some 

 modified form, and suggests, very forcibly 

 the serial homology between the limbs of 

 the same side, and in the normal position 

 (syntropism). Certainly, if we recognize 

 an homology between the very variant ap- 

 pendages of the decapods, we can hardly 

 refuse it in the case of this primitive sala- 

 mander. There is at present the greatest 

 need of a universal set of terms to be ap- 

 plied equally to similar parts in the fore 

 and hind limbs of vertebrates, but this 

 manifestly rests upon the establishment of 



