19,6 Okamoto : Secondary Sexual Characters in Loaches 725 
sue under the dermal layer and in the scale pouches is not ex- 
actly known. I shall investigate this point some time in the 
future. 
(1) Cunningham, J. T. Sexual dimorphism in the animal kingdom. (A 
theory of the evolution of secondary sexual characters.) London 
(1900). 
(2) Geddes and Thomson. The evolution of sex (1901). 
(3) Regan, C. T. Sexual differences in the poeciliid fishes of the genus 
Cynolebias. Ann. & Mag. Nat. Hist. VIII 10 (1912) 641, 
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