304 DISTRIBUTION AND AETIOLOGY OF THE CRAYFISHES. 



the same form need be questioned on morphological 

 grounds. However, Kessler asserts that, in those lo- 

 calities in which A. leptodactylus and A. nobilis live 

 together, no intermediate forms occur, which is pre- 

 sumptive evidence that they do not intermix by breeding. 



No crayfishes are known to inhabit the rivers of the 

 northern Asiatic watershed, such as the Obi, Yenisei, 

 and Lena. None are known * in the sea of Aral, or the 

 great rivers Oxus and Jaxartes, which feed that vast 

 lake ; nor any in the lakes of Balkash and Baikal. If 

 further exploration verifies this negative fact, it will be 

 not a little remarkable ; inasmuch as two t, if not more, 

 kinds of crayfishes are found in the basin of the great 

 river Amur, which drains a large area of north-eastern 

 Asia, and debouches into the Gulf of Tartary, in about 

 the latitude of York. 



Japan has one species (A. japonicus), perhaps more ; 

 but no crayfish has as yet been made known in any part 

 of eastern Asia, south of Amurland. There are cer- 

 tainly none in Hindostan ; none are known in Persia, 

 Arabia, or Syria. In Asia Minor the only recorded 

 locality is the Rion. No crayfish has yet been disco- 

 vered in the whole continent of Africa. 1 



* It would be hazardous, however, to assume that none exist, especi' 

 ally in the Oxus, which formerly flowed into the Caspian. 



f A. dauricus and A. Schrenckii. 



t Whatever the so-called Astacus capensis of the Cape Colony maj 

 e, it is certainly not a crayfish. 



