ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 183 



Variation and Sexual Selection in Man.*— Mr. E. T. Brewster seeks 

 to show that there is a relation between the conspicuousness of any part 

 of the body and its variability as measured by the coefficient of varia- 

 bility of its dimensions. He offers evidence to prove : — (a) that con- 

 spicuous dimensions tend to be more variable than other dimensions, e.g. 

 the nose more variable than the rest of the face, the face without the nose 

 more variable than the head ; and (b) that sexual selection has brought 

 it about that parts of the body tend to be more variable in proportion as 

 they are of greater assthetic value. 



Blind Rat of Mammoth Cave.f — Prof. C. H. Eigenmann and J. R. 

 Slonaker have obtained specimens of this rat, and have studied the habits 

 of the living animal, as well as the structure of the eye. They find no 

 evidence that it is blind, and no marked macroscopic or microscopic 

 difference between its eyes and those of the common grey rat. The 

 retina seemed to be slightly thicker in the cave rat than in the grey rat ; 

 but so far as the structure of the eye is concerned, there seems no reason 

 why the animals should not see perfectly well. 



Blind Fishes of North American Caves.J — Prof. C. H. Eigenmann 

 publishes a series of papers on oertain points connected with these fish. 

 He finds that there are at least six species of Arnblyopsidre inhabiting 

 North America, of which three have well-developed and three vestigial 

 eyes. Those with rudimentary eyes have been derived from normal- 

 eyed forms, but even those with well-developed eyes have these of 

 smaller size and simpler structure than in ordinary fish. The author 

 believes that the condition of the eyes can only be explained as " the 

 result of the transmission of disuse effect." 



In association with A. C. Yoder, the same author has made observa- 

 tions on the ear and hearing power of Amblyopsis. The auditory organ 

 resembles in all" respects that of other fish, but the authors find that 

 there is no evidence that the blind fish, any more than other fish, can 

 hear noises in the strict sense. 



Prof. Eigenmann has further studied the blind fish of the Missouri 

 caves, which has been regarded as identical with the Tyvltliclithys subter- 

 raneus of Kentucky and Tennessee. He finds that the Missouri form 

 constitutes another species, T. rosse, its resemblance to T. subterraneus 

 being merely a case of convergence, due to similar environmental con- 

 ditions. Further, as it would appear from the structure of the eye that 

 the Missouri form has had a different origin from the Kentucky form, 

 the author proposes to erect for the former a new genus Troglichthys. 

 The genus is not defined, and it is not expressly stated whether or not 

 this has been previously done, but the author emphasises the exist- 

 ence of large scleral cartilages, absent in Typhlichthys. 



Moravian Cave Fauna. § — Herr Karl Absolon considers that his 

 observations on the fauna of the limestone caves of Moravia afford an 

 answer to Verhoeff 's |j views on cave faunas generally. These caves are 

 especially characterised by their geographical isolation, and by the 

 presence of members of the Thysanura and Acarida, rare in other caves. 



* Proc. Boston Soc. Nat. Hist., xxix. (1S99) pp. 45-61. 



t Proc. Indiana Aoad. Sci., 1S98, pp. 253-7. % Tom. cit.. pp. 239-51 (H figs.). 



§ Zool. Anzeig., xxiii. (1900) pp. 1-6. || Op. cit., 1899. 



