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, apparently, largely on the weather. The hawk spends a large part of each day on a perch, nearly motionless, except that the head is turned constantly so that the eye may follow every moving object that comes within the range of vision. If food is scarce, the above routine may be very much altered. The soaring flight, if undertaken at all, may be interrupted for hunting at any time, and the perch is frequently changed. During the nesting season, the feeding behavior shows individual, and to some. extent, specific variation. In general, both parents incubate, by turns, and secure their food while off duty. While the young are in the nest, or at least during about the first three-fifths of this time, the male does all the hunting and the female all the feeding and brooding of the young. The male may bring the food to the nesting ledge or hole, or he may transfer it to the female in the air by turning on his back as the female stoops at him from above, thus allowing the female to take the quarry held in his feet. Birds almost always, and mammals and lizards frequently, are headless when brought to the nest. It appears as though the male (particularly of the Duck Hawk) lives largely, if not exclusively, on heads of the prey animals during this period. March, 1936 EATING HABITS OF FALCONS 23

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S c h m a n k e w i t s c h (1875, '77, and elsewhere) came to the conclusionthat the differences between the genera Artemia and Branchipus were entirely the result of differences in the media in which the individuals had grown. He concluded that the change was a gradual one, requiring several generations to change even from one type of Artemia to another, and that the varieties resulting were hereditary and of relative permanence. B a t e s o n (1894), on the basis of S c h m a nkewitschs work, and on some material of his own from Russia, became even more of a direct transformationist. S a m t e r and H e y m o n s (1902), studying collections from the Molla Kary region of the Caspian Sea, concluded that none of S c h m a n k e w i t s c h ' s varieties is valid, and that they are all Artemia salina, more or less degenerated through the effects of salinity, They also concluded that the effects of the salt are not constant and that in the same concentration all forms are to be found. A r t o m (1907), using Artemia from Cagliari under carefully controlled conditions in the laboratory, found that eggs from parents of the ,,Mulhausenii" (M. Edw., now Milhausenii G. Fisch., not Muhlhausenii S. Fisch.) type, if allowed to hatch and develop in brine of 7 O B. (7.26% NaCl) gave only A. salina of ,,tip0 delle basse