THE ANCIENT SILK-TRADERS' ROUTE. 



377 



very scarce, so that, speaking broadly, every bird 

 finds a mate and breeds. But this would almost 

 or quite neutralize any effect of sexual selection, 

 of color, or ornament, since the less highly- 

 colored birds would be at no disadvantage as 

 regards leaving healthy offspring." While ac- 

 cepting this conclusion, we may ask whether the 

 same argument is not capable of further applica- 

 tion ? It is generally stated that the " fittest " 

 male — i. e., the one most in harmony with the 

 circumstances in which he is placed — will have 

 the best chance of securing a mate and of leaving 

 offspring, while the feebler, the slower, the less 

 energetic, and those least in harmony with the 

 situation, will be left in a state of single blessed- 

 ness, and will not transmit their attributes to 

 posterity. But, on the principles laid down in 

 the passage we have just quoted, the effects of 

 natural selection will be greatly neutralized. It 

 must, however, be remembered that the destruc- 

 tion of birds, especially in a state of Nature, will 

 not fall exclusively or mainly upon those which 

 have secured mates, but will likewise extend to 

 the unwedded. 



While combating Mr. Darwin's view, that 

 the brilliant colors of butterflies have been ac- 

 quired for the sake of protection, Mr. Wallace 

 remarks : " It is, in fact, somewhat remarkable 

 how very generally the black spots, ocelli, or 

 bright patches of color, are on the tips, margins, 

 or disks of the wings ; and, as the insects are 

 necessarily visible while flying, and this is the 

 time when they are most subject to attacks of 



insectivorous birds, the position of the more con- 

 spicuous parts at some distance from the body 

 may be a real protection to them." This rule, 

 however, is by no means universal. The fire-wasp 

 (Chryseis), and not a few other Hymenoptera, 

 have brilliantly-colored bodies, but colorless and 

 transparent wings, which, when expanded and in 

 action, are scarcely visible. In numbers of Lepi- 

 doptera the more intense colors, especially reds, 

 are found entirely or mainly on the posterior 

 wings, which extend to a less distance from the 

 body than do the anterior pair. In many cases, 

 again, Lepidoptera, Coleoptera, and Hymenoptera, 

 display conspicuous colors at the extremity of 

 the abdomen, where a blow from the beak of a 

 bird would doubtless permanently disable. 



A question may here arise concerning the use 

 of the coloration of the posterior or true wings 

 in certain beetles, a circumstance not sufficiently 

 examined. While these wings in the vast ma- 

 jority of Coleopterous species are colorless, or, at 

 most, of a very faint yellowish hue, in the Colo- 

 rado beetle they are pink, and purple in several 

 Chrysochroas, Pachnodas, and Lomapteras. Why 

 should these species thus differ from other close- 

 ly-allied forms, with whom they appear to agree 

 most closely in their habits ? 



We have no doubt that Mr. Wallace's formal 

 declaration against the doctrine of sexual selec- 

 tion will attract the attention of disbelievers in 

 evolution, and we venture to hope that all the 

 comments which will be elicited may not be be- 

 side the question. — Quarterly Journal of Science. 



THE ANCIENT SILK-TRADERS' ROUTE ACROSS CENTRAL 



i\SIA. 



T I THE paper on the above subject read by 

 -*- Baron Kichthofcn before the Berlin Geo- 

 graphical Society, on the 5th of May last, was 

 based, in a great measure, on the general views 

 enumerated in the author's recently-published 

 work on China, the more detailed information 

 being derived from Ptolemy and Chinese sources. 

 It opened with a general sketch of Central Asian 

 geography, in which the parts played by the Him- 

 alayan, Kuen-Lun, Tien-shan, and Altai systems 

 were clearly expounded. The Tarim Basin the 

 author likened to a gigantic horseshoe-shaped 

 plain, the sides of which are formed by the Tien- 



shan and the Kuen-Lun. This horseshoe was 

 the western part of a former extensive sea, which 

 was bounded on the north by the Altai Range. 

 Its eastern limit cannot at present be defined with 

 accuracy, but it nowhere trenched on the confines 

 of modern China. One noteworthy feature of 

 this great inland sea, which is even now testified 

 to by the name Han-hai, or " dried-up sea," ap- 

 plied by the Chinese to its former site, was the 

 depression or arm between the Tien-shan or Altai 

 Ranges, by which it communicated with another 

 extensive sea, beginning about Lake Balkash. 

 In the recesses formed by the spurs of the Tien- 



