DIGESTIVE SYSTEM OF PERIODICAL CICADA. 207 



namely, that the storage of potential energy in the form of fats 

 or surplus proteids is an obvious provision for maintenance of 

 vital functions during periods of reduced or suspended activity, 

 but which is made available by a reversed metabolism, brought 

 about by the operation of identical or similar enzymes, as shown 

 below. Greene has, by actual experiments and extended observa- 

 tions during these migrations of the salmon, shown with clearness 

 and convincing results the entire physiological history of the 

 absorption and storage of fats, and its later transportation to the 

 various tissues and organs concerned. He also critically reviews 

 the earlier work of Miescher along these lines and emphasizes its 

 values, at the same time showing certain of its defects, especially 

 its erroneous contention that the fats found in muscular tissues 

 were degeneration products; and shows convincingly that the 

 presence of fat in such tissues is a result of infiltration and "that 

 intracellular fat of the King salmon is an expression of the nutri- 

 tive state of the muscle. It is a loading of fat by a process of 

 infiltration and is not a degeneration of the muscle substance." 

 He next points out the applicability of the same discovery by 

 Kastle and Lovenhart of the reversible action of lipase and, as 

 a consequence, gets an insight into the mode of transportation 

 of fats from tissues to tissues in the animal body. (Ibid., pp. 

 123-125.) These researches of Greene throw fresh light upon 

 very similar problems of reserve energy of storage fats well known 

 in invertebrates. For example, the cases of the Ephemerids, 

 Lepidoptera, and the periodical cicada, all of which show points 

 of close similarity to the foregoing. Among insects, this reserve 

 material is accumulated chiefly in a peculiar organ known as the 

 "fat body" which is "of various shapes," according to Packard, 

 "more or less lobulated and net-like and covers parts of the 

 viscera, also forming a layer under the integumen. The tracheal 

 endings are usually enveloped by the fat body. It is larger in 

 the larvae than in the adults, especially in Lepidoptera, in them 

 forming a reserve nutrition used during the metamorphosis and 

 during the formation and ripening of the eggs and male cells." 

 (p. 419.) According to Wheeler whom Packard quotes, this fat 

 body is of mesodermal origin, and differentiated from portions 

 of the ccelomic walls, hence of metameric origin. Numerous 

 more or less conflicting accounts have been given as to the partic- 



