24 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
in successive generations of females, yet it may become predominant, 
habitual, and hereditary, with transference to the males as well. If the 
transference to the males does not hinder in any way the male reproduc- 
tivity, it may become a constant character, and thus arises a secondary 
similarity of the sexes. But if the transference be in any way antago- 
nistic to the male reproductive functions, those forms which exhibit it 
will be eliminated. 
In established sexual dimorphism the secondary sexual characters 
cease to be mixed, since the essential reproductive differentiation limits 
this both positively and negatively. If the gonads become rudimentary 
the limits arc removed, and one sex may show the characters of the 
other, as in many, perhaps most, casual hermaphrodites. 
The frequently regular occurrence of male and female characters on 
the two sides of the body 'depends upon a preponderance of one half of 
the body. 
Useless organs degenerate not in consequence of disuse, but only in 
consequence of the greater use or development of other organs, by which 
their substance is claimed. 
In Lepidoptera, sexual selection has but a slight role, if any, in the 
phenomena of dimorphism. 
“Bipolarity” in Distribution of Marine Animals.* — Ur. A. E. 
Ortmann begins an interesting essay by stating the general interpretation 
of the similarity between Arctic and Antarctic marine animals. It 
has been expounded especially by Theel, Pfeffer, and Murray, and is 
as follows : — In association with the climatic differentiation which 
occurred at the poles at the beginning of the Tertiary period, certain 
polar members of the universal tropical fauna adapted themselves to the 
change. This adaptation occurred in a similar fashion at the two poles, 
and the gradual cooling having done its work, produced conditions of 
environmental uniformity which inhibited further change. As varia- 
tion continued more abundantly in the warmer waters the distinctions 
between polar and tropical fauna became more and more marked' 
Ortmann objects (1) that there is no warrant for supposing a de- 
creasing transformability in polar animals ; (2) that in many cases the 
similarity of north and south polar forms is secondary, and depends 
upon abyssal migration from one pole to the other; (3) the apparent 
bipolar distribution of deep-sea animals is only apparent, the facts are 
insufficient to warrant the induction ; (4) in some cases the bipolarity 
is due 'to littoral migration from north to south ; (5) the theory breaks 
dow r n entirely when applied to Decapod Crustaceans. 
Contrasts in the Marine Fauna of Great Britain, f — Prof. W. C. 
MTntosh has put together some of the impressions made by an exami- 
nation of the littoral fauna, and that within a few miles of the shore, at 
the four points of the compass in the British area ; for the north, the 
Shetlands, for the south, the Channel Islands, for the east, St. Andrew’s, 
and for the west the Outer Hebrides have been selected. It is, of course, 
impossible for us to analyse a paper which is full of details and names, so 
that we must content onrselves with quoting the conclusion. “ Limited 
* Zool. Jalirb. (Abth. Syst.), ix. (1896) pp. 571-95. 
t Ann. Mag. Nat. Hist., xviii. (1896) pp. 400-15. 
