ing quarters. Mr. J.W.Brock, without knowing that I had just caught a large rat outside the cage, suggested a rat as the possible cause of the night alarms, since the covering of the cage would minimize the probability of its being a horned owl. I do not think that there is any possibility of a rat's having been in- side, though one may have crawled up the wire outside and run over the roof. It is still a mystery. During the last three nights Archie has slept in the bed intended for Terry twice and in his regular one once. Terry was put to bed each night in the place not occupied by A. He will not even look at his old place. No dispute arose between them on account of their being placed in each other's beds on the 16th. On the 18th. Archie again tried to roost for the night on my shoulder when T was already there. Contrary to experience of the 16th., this time Terry repelled him with a sound blow on the wing, calling A to lose his balance and drop to the floor. In discussing with Dr. J.M. Linsdale the sunning habits of the road runner, he suggested that I endeavor to determine with a photometer (of the Weston "Photronie" Exposure meter type) the intensity of the illumination that brings about the reaction. (I had explained to him my conception of the two types of sunning postures: The "hollow bowl" type apparently used with sun of moderate intensity, and the "spread eagle" type seen only (by me) under rather strong sun). As a rough preliminary, this morning (19th) Rhody being present and all three roadrunners being exposed to the same illumination and in plain sight near at hand, I used Terry's back as a standard surface from which to measure the intensity of the light. (It is probable that the best way would be to have some standard surface, such as magnesium carbonate--a good standard of white-- and take continuous readings of the light reflected from it while watching the reactions of the birds.) Terry did not prove a good standard. In the first place, both he and Archie insisted upon occupying my shoulders at the same time when I sneaked up on them with the meter, leaving me foolishly pointing the meter at nothing. In the next place, when he did get down and dispose himself favorably (Archie remaining perched upon me during the whole performance) I found that, even with constant illumination upon him, radiation from him varied according to the extent to which his back was exposed by the parting of his wing coverts, because his wing coverts are better reflectors than his downy back feathers The morning was really ideal for the purpose because clouds were intermittently passing over the sun and the birds were responding like automatic thermostats. Archie, naturally, I could not see well, but when his feathers began to tickle the inside of my ear, I could judge more or less of the extent of his expansion. Terry, at arm's length, and Rhody farther away, I could see plainly. The affair was, of course, very rough. Nevertheless, while as expected, the three birds did not synchronize absolutely simul- taneously. since they have wills of their own and are not mere automata. their responses to the varying illumination accommodat- ly provided by the sun were so nearly alike in time-phase as to furnish a really funny show, especially as they were so serious about it and did not realize how comical they were. One thing was quite clear as to all three birds: Response