vol.4.] Hubbard.— Protectivi Devices in Salamanders. Kil 



in Amblystoma and Chondrotus, for Cope describes it in A. 

 punctatum, conspersum, opacum, talpoideum and copeanum, Chon- 

 drotus paroticus and decorticatus, and at least in .4. opacum the 



tail is swollen in consequence. Cope does not mention this con- 

 dition in Plethodon oregonensis nor in /'. mninti r, though he does 

 describe it in /'. glutinosus. 



The glands of Plethodon secrete a milky fluid which is poured 

 out freely when the animal is stimulated by an induction current, 

 either upon the back or upon the tail. In the same way thej 

 respond to the touch of a drop of acid, to irritation in the form 

 of stroking- with a knife blade, to a forcible holding- of the tail 

 either iu the hand or in the jaws of a snake. That the secretion 

 is acid is shown by its turning blue litmus paper red. It appears 

 not to be mucus, for it is insoluble in water, or in water to which 

 has been added ammonia or caustic potash or salt, whether the 

 solutions are strong or dilute, cold or boiling hot. The glands 

 upon the tail, as well as those from other i-egions of the body, 

 likewise fail to respond to specific stains for rnucus. Thionin, 

 used by Nicoglu to discriminate glands of different character in 

 various European Tritons, stains the sublingual of the cat, the 

 oesophagus of Plethodon and the skin of the earthworm in three 

 minutes, so that the mucus stands out in red violet, upon the blue 

 background of the rest of the cell. Mayer's mucicarmine also in 

 fifteen minutes brings out the mucus in the cat's sublingual red 

 against a pink background. None of the skin glauds of Pletho- 

 don. when treated in these ways, give a mucus reaction. The 

 secretion dissolves at once in a solution of hydrochloric acid. 

 When exposed to the air it quickly hardens into a tough trans- 

 lucent mass. The least trace of it upon the tongue produces a 

 drawing, drying sensation, with an astringent taste. In general 

 the secretion seems to be similar to that of certain glands of other 

 Batrachia, as of Triton cristatus, described by Capparelli. 



Diemyctylus also, when stimulated electrically, yields a copious 

 milky secretion, not merely upon the tail, but very generally over 

 the whole dorsal surface. Batrachoseps, on the other hand, 

 yielded very little. 



Before we take up the question of the significance of these 

 glands, we should consider another phenomenon of quite different 



