I20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



zoans, cestodes, trematodes, and crustaceans. Fishes are destroyed in 

 large numbers sometimes by fungoid diseases ; and enormous numbers 

 of them perish by being stranded in pools, overflowed by high tides or 

 freshets, which later dry up. 



Discussion.— Forbes in his discussion of the " Food Relations of 

 Fresh-water Fishes " notes that : " The soft-finned fishes were not 

 very much more abundant, on the whole, in the stomachs of other 

 species than were those with ctenoid scales, spiny fins, and other de- 

 fensive structures, — an unexpected circimistance which I cannot at 

 present explain" (p. 479). The natural comment upon this remark 

 is that the fact detailed does not need to be explained, only accepted, 

 theoretical bias being cast aside. He goes on to say : " Only the 

 catfishes seem to have acquired defensive structures equal to their 

 protection, the predatory apparatus of the carnivorous fishes having 

 elsewhere outrun in development the protective equipment of the best- 

 defended species " (p. 480). Examining the basis for this statement 

 we find that Forbes examined the stomachs of about 900 adult or 

 nearly adult fishes, and that he found catfishes in five of these 

 stomachs ; darters were identified only four times, whitefish only 

 twice, and round suckers only three times, yet all of these are groups 

 which equal or exceed catfishes in abundance. There is no reason 

 therefore for saying their defenses are unusually efficient ; from the 

 table on p. 113 we see that birds take catfishes in due proportion. 



Some kind of protectedness is claimed for practically every kind 

 of fish, yet we see that all groups of them are devoured by natural 

 enemies, and where data is available, predation seems to be very much 

 in proportion to abundance. This principle is especially evident in 

 depredations upon fishes if carried liack through the life history of 

 these animals ; young fishes are more abundant than adults and they 

 are greedily devoured by many piscivorous animals ; while fish eggs, 

 most abundant of all, are sought by a perfect swarm of predators. 

 The grand principle of predation proportional to population is well 

 supported by the known relations of fishes and their foes. 



Amphibia (Salamanders, Toads, Frogs) 



Protective adaptations. — All amphi])ians have skin glands that se- 

 crete a slime which some have thought to function jjartly as a defense. 

 Toads in particular, frogs to a lesser extent, possess poison glands 

 also, and " experiments have proved that toad poison injected into the 

 system will kill any vertebrate, the dose being pr()])ortionate to the 

 size of the animal." (Dickerson, Mary C, The frog book, p. 17, 



