278 DR. H. GADOW ON EVOLUTION [Mar. 20, 



at Oaxaca itself it was joined by the spotted, rather bi-ightly 

 coloured G. hocourti. Thus the Ciiemidophorus-i-Minn, showed a 

 very diflerent aspect in the east, south, and north-west of the 

 triangle examined during my iirst journey. 



On the second journey, chiefly in the States of Morelos and 

 Guerrei'o, the aspect was again diflerent. There are no Cnemido- 

 2)hori in the Valley of Mexico. They were not met with until 

 I had crossed the high range of mountains which separate the 

 Central plateau from Morelos. The only Cnemido])hori at 

 Cuernavaca were the partly sti'iped, partly marbled or slightly 

 cross-bai-red variation of C. mexicantts, var. balsas, and such 

 specimens were traced southwards to the Rivei- Balsas and up 

 again to Chilpancingo in Mid-Guerrero. In the hot valley of the 

 Balsas itself it associated with 0. dejipei, which was, however, 

 rather differently coloured from any of those met with in 

 Oaxaca ; it disappeared long before the backbone of the Sierra 

 Madre del Sur upon which Chilpancingo lies ; but on descending 

 the southern slope, the upper limit of the TieiTa caliente 

 was marked by the reaj)pearance of C. depjjei, and by a lai'gei- 

 striped form which recalled C. itmmitabilis, and any doubt about 

 this was set at rest at a still lower level, where these two kinds 

 persisted down to the Pacific coast. 



All this was sufticient to rouse my interest, and I did not 

 miss many opportunities of at least trying to secure as many of 

 these lizards as possible. It was not easy. Only at a few places 

 did I receive real help from the Indians. In 1902 I caught 

 the lizards, by hand, with nooses or with whips, a procedure which 

 often reduced my party to utter exhaustion. Shooting with a 

 pea-rifle was naturally not very successful. In 1904 I took 

 Dr. Meek's hint and provided myself with a small j^istol and 

 shot-cartridges, and thus I secured hundreds of creatures which 

 otherwise would have escaped. Still, even this was hard aiid un- 

 certain work. When, as in Gueri-ero, during the rainy season a 

 dense mass of herbs springs up almost eveiywhere, no ground- 

 lizard can be seen except in the nai'i'ow tracks across which they 

 flit, to hide in the tangle, warned by our approach. Moi-eover, 

 they are very local and they do not always apj)ear. Rain, certain 

 winds, or a dull sky keep them in their lairs. One may ride for 

 days and not see a single specimen. Then suddenly ther-e may be 

 hundreds, and what are really members of one clan or even of a 

 smaller family may be collected. The next few days again may yield 

 nothing or only a single specimen here and there; and this is I'eally 

 worse than nothing, since it leaves it undecided whether its 

 charactei's are truly typical of that district, or mei-ely individual. 



We collected in the States of Oaxaca, Moi-elos, and Guei-rero 

 some 250 specimens. An enforced prolonged stay in the hos- 

 pitable house of Professor Whitman in Chicago enabled me to 

 examine about 200 specimens in the Field Museum of Nat. Hist., 

 mostly collected by Dr. Meek in regions which I have not visited 

 myself, but about which he could give me valuable information 



