124 Transactions of the Royal Canadian Institute. [vol. x 



been fertilized.) In Plethodon the instinct is more delicately adjusted. 

 This is shown in the marked preference for some particular log as a site 

 for egg-laying. For instance, one small plot of woodland was found to 

 contain Plethodon in abundance during the spring of 191 3 and was 

 visited on June 21st in the search for eggs. A dozen or more rotting logs 

 yielded only males or sexually immature specimens ; at last one log was 

 found which, though apparently not differing from the others, yielded 

 eleven females with eggs. A number of similar cases have been met with. 

 The logs so greatly preferred are invariably conifers, but other factors 

 must enter into the quest on for another coniferous log that seems quite 

 similar may be close at hand yet be entirely destitute. Equally striking 

 is the difficulty that has been experienced in getting females to lay eggs 

 in a terrarium. The thin, almost translucent ventral wall of the abdo- 

 men allows the easy recognition of females containing eggs almost ready 

 for deposition. If pieces of the logs in which the animals have been 

 found are brought from the field and the pieces piled together in a terra- 

 rium so as to reconstruct roughly the log, there is no difficulty in keeping 

 the animals alive and in good condition for long periods. They will feed 

 readily on small insects, e.g., aphids; but, like most amphibia, seem to 

 suffer little from long deprivation. Three specimens overlooked in a 

 small terrarium last spring lived until the end of September with no 

 attention; at the end of that period their physical condition and vigor 

 V ) had suffered so little that they could not be recognised after being allowed 



to mingle with others brought in from the field. In spite of this apparent 

 easy acceptance of life in a terrarium, the change usually is sufficient to 

 inhibit the egg-laying reactions, and the eggs are retained and absorbed 

 during the next five or six weeks. Exceptionally they will be laid as 

 under natural conditions, but only when the female has been brought 

 from the field not more than three or four days before the time for egg- 

 laying. It is not a question of previous impregnation or its lack, for as 

 far as examined, all mature females have been found to have the recep- 

 tacles filled with sperm some time before the egg-laying season arrives. 



The character of the season has some influence on the depth beneath 

 the surface at which the eggs are laid ; in damp seasons they will be for 

 the most part but an inch below the surface, in dry seasons they will be 

 four or five inches below. This refers to the character of the season up 

 to the time of egg-laying, not after. 



The retention of one egg in the ovary was mentioned in the earlier 

 paper. Later experience has confirmed the observation. The egg is 

 always much under-sized and occurs in about one third of the 

 females accompanying clusters of eggs in early stages of development ; 

 it is then rapidly absorbed, and must have considerable value as a 



