arrangements should be made for nocturnal animals, regardless of their visibility to visitors, if their preservation is of importance. The hygiene of communicable disease has influenced everyone to use concrete and metal for cages. These substances are without doubt most simply kept clean, but they are heat-conducting and remain cold or damp longer than wood or the ground. It may be claimed that the latter two cannot be disinfected so well, but this need not militate against their use. Wood can be disinfected by sunlight or by mechanical cleaning plus disinfectants, by a blast lamp and by paint. The ground will disinfect itself if allowed to lie fallow for a time, or it may be turned over after sprinkling with lime. It is fair to note that the New York Zoological Garden reduced their mortality, especially from verminous pneumonia, by changing some deer herds to concrete paved enclosures; if that were the only change made the result would be very significant, but it should not be forgotten that another clean ground range might have served as well to a herd from which the infected ones had died. My own observations with guinea-pigs, rabbits, mice and dogs lead me to believe that they thrive and breed better on wooden floors than on metal or stone. I have tried to work out figures to show that more animals die when housed in enclosures of stone and metal than when upon the earth or on wood, but the attempt has been unsuccessful chiefly because of the presence of epidemics and parasites, principally among the birds. The attempt was further embarrassed because some members of an order are housed on both floorings. However, there was no great advantage for the metal and concrete floors even after the epidemic had been discounted. This Garden does not have a great number of pneumonias, a disease said to be favored by dampness and cold, but those that occur are chiefly among the small mammals, on wooden floors and in the large bird house in cages of concrete and metal. However, the construction of both these houses permits the visitors to approach very close to the cage, a factor that doubtless explains the disproportionate incidence of inflammation of the lungs. In so far as outdoor fowl and ungulate ranges are concerned, they should be changed frequently under the best conditions since occasionally one will find groups doing badly until moved. Moreover the ground becomes contaminated with parasites such as esophagostomum and heterakis, infestation with which while not very serious in itself, may lead to fatal infection with bacteria.