The facts about the longevity of fish are not very numerous, but it seems clear that these animals reach a great age. The ancient Romans, who used to keep eels in aquaria, have noted that these fish would live for more than sixty years. There is reason to believe that salmon can live for a century, whilst pike live much longer. There is, for instance, the much quoted instance of the pike stated by Gessner to have been captured in 1230 and to have lived for 267 years afterwards. Carps are regarded as equally long lived, Buffon setting down their period of life as 150 years. There is a popular idea that the carp in the lakes at Fontainebleau and Chantilly are several centuries old, but E. Blanchard throws doubt on the accuracy of this estimate, inasmuch as during revolutionary times most of the carp were eaten when the palaces were overrun by the populace. There is no doubt, however, that the life of carp may be very long indeed. Not very much is known about the duration of life in batrachians, but it is certain at least that some small frogs may live twelve or sixteen years, and toads as many as thirty-six years. More is known about the life of reptiles. Crocodiles and caymans, which are large and which grow very slowly, attain great ages. In the Paris Museum of Natural History there are crocodiles which have been kept for more than forty years without showing signs of senescence. Turtles, although they are smaller than crocodiles, live still longer. A tortoise has lived for eighty years in the garden of the Governor of Cape Town, and is believed to have reached the age of two hundred years. Another tortoise, a native of the Galapagos Islands, is known to be 175 years old, whilst a specimen in the London Zoological Gardens is 150 years old. A land tortoise (_Testudo marginata_) has been kept in Norfolk, England, for a century. I am informed that in the Archbishop’s palace at Canterbury, there is to be seen the carapace of a tortoise which was brought to the Palace in 1623 and which lived there for 107 years.[38] Another tortoise, brought to Fulham by Archbishop Laud, lived in the Palace for 128 years. I have already referred to a specimen of _Testudo mauritanica_, the history of which is known for 86 years, but which is probably much older. Very little is known as to the longevity of lizards and serpents, but it may be inferred from what I have said about other reptiles that reptiles as a class are able to reach great ages. It is an easy inference that the great duration of life in cold-blooded animals is associated with the slowness of the physiological processes in these creatures. The circulation, for instance, is so slow, that the heart of a tortoise beats only 20 to 25 times in a minute. Weismann has suggested that one of the factors influencing the duration of life is the rapidity or slowness of the vital activities, the times taken by the processes of absorption and nutrition.