164 THE POPULAR SCIENCE MONTHLY. 



every prominent feature of their homes was reproduced. I found 

 that at 120° Fahr., with the atmosphere perfectly still, they in- 

 variably sought shelter, clustering in one cooler and dark corner ; 

 but at 100° they were exceedingly active, particularly if hungry, 

 and made no effort to avoid the direct rays of the sun. 



When exposed to a sudden transition from a very high to a 

 low temperature, they quickly became inert, and, as the warmth 

 was allowed to increase, it was instructive to see the sluggish 

 movements of both the lizards and the imprisoned flies give way 

 to more active ones, which culminated in the restored suppleness 

 of the reptiles being equal to the capture of the swiftly darting 

 insects. Forced exposure, for a period of three hours, to a tem- 

 perature of 135°, caused death in four instances, and brought about 

 a condition akin to aestivation in nine specimens thus exposed. 

 As the pine-tree lizards are always found in localities where there 

 is adequate shelter from excessively high temperature, it is not 

 probable that aestivation ever occurs, as it does occasionally among 

 some of our wild mice ; but it is interesting to note that a condi- 

 tion closely allied to it can be artificially produced. 



The conclusion reached by both field observation and experi- 

 ments was, in brief, that when the temperature is such that those 

 forms of insect life upon which they depend become inactive, the 

 lizards withdraw to their shelters and likewise remain quiet if 

 not asleep, this period of inactivity extending over several days, 

 as during the prevalence of a northeast storm, or a protracted 

 " spell " of cool and cloudy weather. Again, experiments with a 

 large number in confinement showed that when kept without 

 food at a low temperature, they lived for many days, while a 

 like number starved in a short time when a high temperature 

 was maintained. This lizard, therefore, appears to be one origi- 

 nally belonging to a tropical climate, that has gradually become 

 adapted to a temperate and variable one. 



The normal coloring of the pine-tree lizard is distinctly pro- 

 tective. Whether this has been gradually acquired or not, it is 

 certain that it now renders the animal quite inconspicuous. Par- 

 ticularly when it is resting upon a rough-barked tree is this true ; 

 and one of my first objects, in studying the species in its native 

 haunts, was to determine how far the markings were changeable 

 and under their owner's control. Many specimens were found to 

 be quite dark — indeed, almost black — while others were so light 

 that the undulating transverse bars upon the back were very dis- 

 tinct and discernible at a considerable distance. This difference, 

 I am quite sure, bore no relation to the surroundings ; and the 

 specimens subsequently collected and kept under daily observa- 

 tion for nine weeks practically retained the light or dark color- 

 ing they possessed, at the time of capture. In confinement many 



