1914] The Egg-Laying Habits of Plethodon Cinerevs. 121 



THE EGG-LAYING HABITS OF PLETHODON CINEREUS 

 By W H. Piersol, B.A., M.B. 



(Read 15th November, 1913.) 



Two accounts of the natural history of this, our commonest sala- 

 mander, have' appeared, one by Miss M. E. Cochran (1911) and one by 

 the writer (1909). Both agree in their descriptions of the eggs, but 

 neither gives any information as to the mode of deposition. The writer 

 has sought to determine this by observations made on Plethodon both 

 in its natural habitat and in a terrarium. The following is an account 

 of the more important observations together with comment and infer- 

 ence. Fertilization is internal; this had been predicted in the earlier 

 paper (1909) and has since been confirmed by the fact that a female 

 isolated in a terrarium for four days laid eggs that developed naturally. 



Case I. On one occasion the actual extrusion of the eggs was ob- 

 served. The female had been placed when captured in a small glass jar 

 along with fragments of the log in which she was found; and the jar with 

 others containing eggs was carried back to the laboratory in a small bag. 

 Chiefly for the sake of the eggs which are very delicate the bag was guarded 

 from shocks as far as possible, then for another hour it stood unopened. 

 On removing the jar from the bag it was seen that the egg laying had just 

 begun, fortunately in such a position that all its details could be observed. 

 The lips of the cloaca are pressed against the surface from which the 

 eggs will eventually hang and a small quantity of mucus is extruded and 

 adheres firmly to it. This much had been completed before observation 

 began so nothing can be said as to the interval that then elapses before 

 the first egg is laid. The extrusion of each egg occupies about twenty 

 seconds and an interval of five to ten minutes occurs before the next 

 appears. The first three eggs were laid in contact with the mucus above 

 mentioned; the fourth, and last, adhered to them in turn through the 

 stickiness of the egg-envelopes. As the female did not move during the 

 entire process, all the eggs were laid at the same point, each egg as it 

 came, crowding the preceding ones aside, thus making sure of being in 

 contact with them. For over an hour after the last egg was laid the 

 female did not change her position; during the next hour she left the eggs 

 a few minutes, then returned and coiled herself about them. 



