WOTTON : LIFE-HISTORY OF ARION ATER, 



i6i 



The time required for hatching varies considerably, and 

 is largely influenced by circumstances and surroundings. In 

 the case under notice it varied from sixty to seventy-four days. 

 The time is prolonged by dryness and cold, a continued dryness 

 being fatal to the embryo. Extreme cold and extreme heat have 

 a like result. I have frequently exposed them during a hard 

 frost, but none of the eggs so treated ever produced young. 

 The minimum time is reached in warm, damp situations, when the 

 young slug is sometimes excluded in forty days. 



It will be as well to mention here that the eggs deposited 

 in one batch — even if within an hour or so of each other — do 

 not hatch simultaneously as may be supposed, the intervening 

 time being often several days. 



Here are the particulars of one deposit which may be taken 

 as a fair example : — 



Dkposited by Light-Yei.low Arion. 



/vr. 



Nov. 30th, iSSg. 

 loi Ejrcs. 



The remainder were unproductive. 

 About ten or twelve days before the baby Arion emerges, 

 the eggs begin to turn yellow, which deepens as time goes on. 

 They also get more opaque. Under a low power the slug can 

 be seen moving inside the shell, and it is most interesting to 

 watch its introduction to the world. This is best seen by plac- 

 ing the egg on a looking-glass. The inmate gradually increases 

 in size until a fine crack becomes visible; this gradually enlarges 

 until the shell is split up, or one of the ends opens, and the slug 

 is able to crawl out. Some of them, when nearly clear of the 

 shell, will back or crawl into it again, and curl themselves up 



