308 SUMMARY OF CURRENT RESEARCHES RELATING TO 



cutis. Four kinds of movement may be distinguished in these cells : — 

 Ciliary movement, the amoeboid movement of wandering cells, the 

 irregular and regular|i,streaming of granules — the former in the outer 

 layer of epithelium and the latter in the melanospores of the cutis. The 

 author poiuts out that the tadpole's tail is admirably suited for 

 demonstration purposes. J. A. T. 



c. General. 



Variation in Deer-mice. — F. B. Sumner (Amer. Naturalist, 1918, 

 177-208, 290-301, 439-54, 13 figs.). A study of the structural and 

 pigmentary differences distinguishing four geographical races of Fero- 

 myscus manicidatus. The pigmentary differences, show a general 

 correlation with enviromental features ; the structural differences do 

 not. All the differences are differences of degree, revealed through a 

 comparison of mean or modal conditions rather than of individuals. 

 These subspecific differences are hereditary. They persist when 

 environmental conditions are interchanged. Hybrids between even the 

 most divergent of the four races are predominantly intermediate in 

 character, both in the F^^ and the Fg generations. In contrast to the 

 sensibly continuous variation and sensibly blended inheritance shown in 

 respect to these subspecific characters is the behaviour of certain 

 "mutations." Here are seen typical illustrations of discontinuous 

 variation and inheritance of the strictly alternative or Mendelian type. 

 There are two types of variation and inheritance. J. A. T. 



Androgenic Origin of Horns and Antlers.— J. F. van Bemmelen 

 {Proc. K. Akad. Wiss. Amsterdam, 1918, 21, 570-5). According to 

 Weber and others, horns and antlers were originally common to both 

 sexes and were defensive weapons against enemies. Later on they 

 came to be used more and more in the contests of rival males, and have 

 become exclusively masculine features, or at least more strongly developed 

 in the males. This is in agreement with the view of Tandler and Gross 

 that all secondary sex features were originally specific characters. To 

 van Bemmelen the opposite view seems more justifiable that the head 

 armature arose in males as a means of attack in their duels for the 

 females, and afterwards passed to the females. Among his arguments 

 are the following : — In deer the antlers are absent in all females except 

 the reindeer, where there may be a non-sexual function ; in those antelopes 

 that have horns in the female sex as well as in the male, the horns of 

 the females are usually smaller, and those of the males show a tendency 

 to hypertrophic and exaggerated growth not consistent with the require- 

 ments of practical use ; similar exaggerations, e.g. the four-horned 

 goat, are known in cattle, sheep and goats; in giraffes with small 

 pedicle and small os cornu, the males have higher and stronger horn- 

 stumps than the females, and they have the unpaired nasal knob ; 

 in the Okapi the horns are primarily absent in the female ; the annual 

 shedding of the antlers and their regrowth in Cervini\3 are apparently 

 connected with rut ; the same appears to be the case in Antilocapra ; the 

 bony processes on the head of giraffes, Suidas, and extinct forms cannot 

 reasonably be regarded as practical weapons, they are far too cumbrous 



