286 THE VARIATION OF ANIMALS IN NATURE 



5. Snout of desert Blind Snakes {Hewitt, igi4, p. 11). 



Hewitt states that Typhlosaurus lineatus and Typhlops schiuri 

 1 are both separated from their allies by the possession of a 

 sharp cutting snout enabling them to burrow in the sun-baked 

 soil of the Kalahari.' Mr. Hewitt is an extremely competent 

 observer, but we feel that the critical differences are too 

 summarily expressed to be of much value. To begin with, 

 there is no statistical statement of the frequency of occur- 

 rence. Next, Mr. H. W. Parker informs us that, at least 

 in Typhlops, the sharp snout tends to occur sporadically 

 throughout the genus, even in individuals of species normally 

 not possessing it, and no one has suggested a general correlation 

 between it and the desert habitat. Mr. Parker informs us 

 that a similar snout occurs in species of the Amphisbaenid 

 Agamadon in areas (W. Africa, S. America) which are not 

 characterised by desert. Lastly, we are inclined to be rather 

 suspicious of Mr. Hewitt's ' sun-baked soil ' of the Kalahari 

 and to express the surmise that other soils than those of deserts 

 become ' sun-baked.' 



6. Attachment of ticks to their hosts {Nuttall, iqii, p. 54). 



Nuttall states that in the Argasidae Ornithodorus megnini, 

 which remains for a long time attached to its host as a nymph, 



Fig. 26. — Hypostomes of Larval and Adult Ticks of the Genus Argas, 

 to illustrate Differences in Armature. 



a. A. persicus larva (similar in larva of A. reflexus). 



b. A. vespertilionis (larva). d. A. reflexus (adult). 



c. A. persicus (adult). e. A. vespertilionis (nymph). 



(After Nuttall, 191 1.) 



