The effect of captivity is felt in another way. A very large percentage of wild life perishes during the first weeks or months after its capture, and in gardens the heaviest mortality occurs among the recent arrivals. The London Garden figures that from thirty-three per cent. to fifty per cent. of their total mortality is in animals that have not been in the garden six months and that die because they are not yet accustomed to their new surroundings. It seems to us, both from an academic and a practical standpoint, that this is a long time and should afford ample opportunity for the garden to study the specimen and for the specimen to become acclimated. These early deaths are perhaps to be ascribed in large part to failure of acclimatization but many are doubtless the result of infection acquired in the wild, in transit while in the hold of vessels, at quarantine, or in trains, or at the establishments of dealers. We have seen a few deaths which have followed behavior that might be likened to homesickness. Perhaps the age at arrival has an influence upon the morbidity and mortality of wild animals, for it is easily conceivable that the young and the very old might adapt themselves to new surroundings with much less readiness than the sturdy middle-aged adult. The age of animals upon arrival is very rarely known, and can only be recorded as “young,” “fully developed,” and “old.” This will have an effect upon statistics and when possible is noted in the text, but this is not practicable to the extent we desire. The meaning of “young,” “adult,” and “old” is not the same throughout the animal orders nor even within orders. Mitchell[3] has attempted to gain concrete ideas of the expectancy of life among animals by analyzing the records of the London Gardens. This gentleman bases his figures upon known ages and the length of time in captivity, from a combination of which data the specific viability and the potential longevity may be estimated. Such results, he admits, can only be approximate and they show within classes and orders, a decided lack of uniformity. The terms “specific” and “potential” longevity, coined by Sir Ray Lankester, apply, for the first, to the average length of life as it is affected by external conditions and those incident to procreation, while, if an animal be under ideal conditions it will attain the potential longevity which is longer than the former. These considerations have a biological and economic importance, while a knowledge of the pathology shown by the various groups may help to explain these durations of life. Contrariwise figures of the expected longevity may assist us in evaluating youth and senility in the causes of death but can hardly affect the comparative nature of the lesion.