1908.] 



DR. KNUD ANDERSEN ON BATS. 



259 



than in the light colour type, and (2) much less developed in 

 the northern than in the southern races, I conclude that the 

 former, also in this respect, occupy a rather lower stage in the scale 

 of evolu.tion*. 



Diagram showing the percentage of individuals, in some races oi Artiheus Jamai- 

 censis, in which the supraorbital stripes are distinct, strong, or very strong. 



Concluding remarks on the colour. — The facts recorded above 

 may be briefly summed up as follows : — Adult and aged indi- 

 viduals are dark smoky brown on the upper side (dark extreme), 

 or Yandyck-brown (intermediate stage), or Front's brown (light 

 extreme), or some shade of brown intermediate between these 

 three. Dark colour is, in all races, more common in younger 

 adults than in aged adults. Dark-coloured individuals are pre- 

 dominant in A . j. parvipes, i/ucatanicics, jamaicensis, and cequa- 

 torialis ("northern" races), light-coloured in A. j. lituratus and 

 pahnarum (" southern " races). Facial stripes are commoner and 

 more strongly developed in aged individuals than in immature 

 and young adults ; commoner and more sti'ongly developed in 

 light-coloured than in dark-coloured individuals ; commoner and 

 stronger in the southern races than in the northern. There is a 

 certain correlation in the development of supra- and infraorbital 

 stripes : when the former are strong, the latter ai-e as a rule 

 rather well marked or, at least, not quite obsolete ; when the 

 former are i-ather indistinct, the latter are as a rule wanting. 



* Generally speaking, facial stripes are no doubt a very primitive feature among 

 Vertebrates, going back, as it does, to Reptiles (and being present in a vast number of 

 Birds). But each particular case cannot, of course, be considered only from this 

 general point of view. As a matter of fact, the young individuals of A. jamaicensis 

 s. lat. have, as pointed out above, the facial stripes much less developed than the 

 adults, and we are therefore compelled to assume that this primitive feature has, for 

 some reason or other, been lost in that type of Bat (or its predecessors) from which 

 the \Wm^ A. jamaicensis originated, and that now there is again a tendency to 

 reversion to the old feature in adult individuals. 



