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



at Oaxaca itself it was joined by the spotted, rather brightly 

 coloured G. hocoiirti. Thus the Cnemidophorus4ax\n& showed a 

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

 triangle examined during my first journey. 



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

 Guerrero, the aspect was again different. There are no Cnemido- 

 2)hori in the Yalley 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 Cnemidophori at 

 Cuernavaca were the partly striped, partly marbled or slightly 

 cross-barred variation of C. mexicanus, var. balsas, and such 

 specimens were traced southwards to the River Balsas and up 

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

 Balsas itself it associated with C. deppei, 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 Ohilpancingo lies ; but on descending 

 the southern slope, the upper limit of the Tierra caliente 

 was marked by the reappearance of C. de202)ei, and by a larger 

 striped form which recalled C. immuiabilis, 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 sufiicient 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 pistol and 

 shot-cartridges, and thus I secured hundi-eds of creatures which 

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

 certain work. When, as in Guerrero, during the rainy season a 

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

 lizard can be seen except in the narrow tracks across which they 

 flit, to hide in the tangle, warned by our approach. Moreover, 

 they are very local and they do not always appear. 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 there 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 thei'e ; and this is really 

 worse than nothing, since it leaves it undecided whether its 

 charactei's are truly typical of that district, or merely individual. 



We collected in the States of Oaxaca, Morelos, and Guerrero 

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

 pitable house of Professor Whitmaii in Chicago enabled me to 

 examine about 200 sjoecimens in the Field Museum of ISTat. Hist., 

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

 myself, but about which he could give me valuable information 



