110 Investigations on the Life- History 



muscles alongside the spinal axis in the tail, which serves as reserved 

 material for the nutrition of the animal, as well as the formation of 

 the generative products, while it passes into a torpid state during the 

 dry season and encloses itself into a cocoon. 



Parker (*) supposes, on the authority of Professor 1 Ziegler, that in 

 Protopterus the lateral muscles in the tail undergo fatty degeneration. 

 He also notices a granular degeneration such as is described by Schneider 

 (t) in the case of Petromyozon fluviatilis. The general appearance of 

 the changes in the muscle fibre resembles that described by Fraser and 

 Bruce (in the case already referred to), inasmuch as " the disintegra- 

 tion occurs in small islands in a muscular fibre." Parker thinks that 

 in Protopterus there appears first a fibrillar change causing a loosening 

 of the muscular substance, followed by a granular degeneration which 

 is probably the precursor of fatty degeneration. 



But, as his observations were made only on specimens in the torpid state 

 (and almost all obtained in July), it would be hardly satisfactory to 

 come to any definite conclusion as regards the nature of the muscle-fat 

 without a comparison of the appearances of the muscle before and 

 after the torpid period, and also at different stages of the same. 



In my specimens of the muscle of salmon (which, as already men- 

 tioned, were taken from fish of different times of the year) I did not 

 notice any granular change. 



It is probable that Protopterus passes into the torpid state with its 

 muscles loaded with a store of fat, which is steadily consumed during its 

 captivity. On this supposition the " fibrillar change " is quite explicable, 

 as will be shown later on, in the case of the salmon. 



On the assumption of actual degeneration of muscular tissue, Parker 

 suggests the probability of the re-absorption of the degenerated 

 products, in Protopterus, lamprey and salmon, being brought about by 

 the agency of wandering leucocytes, after the manner described by 

 Metschnikoff (J). But, at the same time, he recognises the difficulty 

 in the acceptance of such an explanation ; as, Loos () has pointed out 

 that MetschnikoiFs researches regarding the part played by leucocytes 

 in the absorption of tadpole's tail are not conclusive. Whereas, in the 

 case of the salmon, the explanation is rendered invalid by the fact of 

 its depending on data that, I contend, still remain not proven. 



" Fatty degeneration " is at pi-esent a misnomer. This investi- 

 gation and similar other observations strongly suggest that, in many 

 cases, the so-called fatty degeneration is a mere fatty infiltration due to 

 increased accumulation of fat from diminished utilisation in the tissues. 

 Bearing in mind the result of chemical investigation, the appearance in 

 the Figures 1, 2, and 3, at all events, should be de-cribed as inter- 

 fibril lary infiltration of fat. It has already been stated that Figure 

 3 is from a fish fresh from the sea one that had been actively feed- 

 ing, and consequently its blood and lymph were rich in fat, whence, in 

 all probability, the muscle cells absorbed fat and stored it between the 

 fibrils. We know thf>t a dense network of capillaries surrounds the 

 muscle fibres, and although no capillaries enter the fibres, there are 

 lymph spaces surrounding Conheirn's areas and communiciting with 

 those beneath the sarcolemma. As already pointed out, the fat granules 

 in fish leaving the sea are more crowded immediately under the 

 sarcolemma (Fig. 3.). Figure 2 is from a late fish one that had 

 been actively using up the reserve fat, hence the transverse section of 



(*) " Anatomy and Physiology of Protopterus Annectens." Transactions of the Royal 

 Irish Academy. Vol. XXX., Part III., p. 207. 



(t) Beitrage zur vergl. Anat. u. Entwickelungsgesehichte d. Wirbelthiere, Berliu, 

 1879. 



(t) " Untersuch ueb. die mesodermalen Phagocyten einiger Wirbelthiere." Biol. 

 Centralblatt Bd. III. 



() Biol. Centralblatt, IX., 1889. 



