The rate of digestion in cold-blooded vertebrates. The influence of season and temperature

A LTHOUGH the been the subjec digestive glands of the lower vertebrates have t of numerous histological researches, and the digestive activity of the secretions of these organs has often been tested, there has bleen until now no attempt to gather data on the actual and relative digestion power of the different groups of vertebrates. It is possible, moreover, to derive the latter kind of data neither from the findings recorded in the works just mentioned nor from the very vague natural history observations bearing on this subject. Certain phenomena already reported by me 1 and having to do with digestion processes which occur perio,dically at the periphery of the growing ova of many vertebrates have primarily led me tc make the present inquiry as to the digestion powers or capacitiec of members of three groups of lower vertebrates, and to determine the influence of sea.son and temperature upon the rate of digestion in these animals. These data promised to be of value, too, ( I) as supplying a measure of the functioning capabilities of the digestive organs of forms occupying different positions in the vertebrate series ; and the fixing of a definite value to the influence upon this process of (2) season and of (3) temperature. The results seem to justify this expectation. They give, furthermore, considerable support to a proposition that was quite unexpected, and which is possibly of considerable import, namely, that as the lower cold-blooded vertebrates were evolved intc the higher cold-blooded forms the latter progressively lost in digestion capacity. A full discussion of the importance of a gradual decline of diges-