[83] THE EVOLUTION OF THE FINS OF FISHES. 1063 



man, disproportionally small, as compared with the rudimentary front 

 limbs, and present only as a pair of minute papilliB. 



The rapid and accelerated outgrowth of the hind limbs of the em- 

 bryos of Anura becomes partially explicable on the ground that the 

 disintegration or rapid metabolism, involving the tail, which occurs 

 during their larval metamorphoses, happens very near the point where 

 the hind limbs are to grow out, and thus places in close proximity a 

 supplj' of available protoplasm, ready to be used in thus precociously 

 accelerating the outgrowth of these appendages, which probably repre- 

 sent, in part at least, the reintegrated substance of the tail, which had 

 developed so far as to have a chordal and a nervous axis, together with 

 a long series of myotomes on either side before its singular retrogres- 

 sive metamorphosis began.* 



The part played in this metamorphic process by certain cells, denom- 

 inated phagocytes by M. Metschnikoff, is very significant, and his con- 

 clusions, as given in a short extract below, as bearing upon pathological 

 phenomena involving muscle and nervous tissue, in such cases as were 

 long before described by Rayer (M6m. de la Soc. Biol, de France), are 

 of the highest interest. Not less interesting to the writer are the con- 

 clusions of Metschnikoff as illustrating the possible origin of the vaso- 

 motor system in the way in which it has been discussed above, since he 

 speaks of " a struggle between phagocytes and septic material." This 

 struggle implies that the phagocyte includes a sensitive center or re- 

 flex sensorium lodged somewhere in its substance, in virtue of which 

 it practically manifests reflex actions like an organism of the Protozoan 

 grade. In the metamori)hosis of the Batrachian tail, which is literally 

 eaten up phagocytically, so to speak, by internal wandering cells, we 

 have an instance of the normal exhibition of phagocytic action. 



"The tail of the Batrachia, during the early stages of its absorption, 

 contains a number of cells, which, when left undisturbed, throw out fine 

 radiating pseudopodia; these contained remnants of nerve-fibers and 

 muscle-cells. Phagocytes, then, play as important a part in the meta- 

 morphosis of Batrachians as of Echinoderms ; and pathologists have af- 

 forded evidence of their agency in the so-called active degeneration of 

 muscles and nerves. 



"The author has tested in a Triton the theory he holds as to the phe- 

 nomena of inflammation in Invertebrates being primitively nothingmore 

 than a collection of phagocytes assembled to devour the exciting object. 

 He touched the point of the tail of a Triton with a small piece of nitrate 



*To what extent I may have restated in the two preceding paragraphs, in another 

 form, what E. Ray Lankester has said before me in his book on Degeneration, or 

 what Dohrn has stated in his essay entitled Der Ursprung der Wirhelthiere und das 

 Frincip des Functionsivechsels, I do not know ; but I have ventured to give the preced- 

 ing examples in order to illustrate the reciprocal relation existing between degenera- 

 tive processes involving transient organs and the formation of permanent ones, with- 

 out having previously read either of these authorities, or knowing what their general 

 ■conclusions were. 



