l62 WOTTON : LIFE-HISTORV OF ARIOX ATER. 



within. There they rapidly increase in size and soon force the 

 shell completely off. After lying perfectly still for a time, it 

 will erect its head, turn it about and survey its surroundings 

 in a manner most amusing to witness. After a little more 

 manoeuvring, it crawls away and betakes itself to the damp 

 earth, where it soon sinks beneath the surface. Here the young 

 Arion remains for four or five days without attempting to take 

 food. When it reappears above ground to commence the re- 

 sponsibilities of life it has increased to nearly double its 

 original size. 



The average length of the Arion immediately after its ex- 

 clusion from the egg is 9 mill. ; in five months it increases to 

 56 mill. After this time it grows less rapidly and attains its full 

 size about the middle of the second year. 



The young slugs are light in colour at first, but the colour 

 is subject to variation ; it usually, however, gradually gets 

 deeper until the animal has attained the age of four or five 

 months, when it becomes permanent. When the Arion is about 

 seven or eight days old, the dark lateral lines appear, but these 

 are not always constant, for they soon disappear again from 

 some individuals, whilst others retain them. The fringe around 

 the foot also alters or graduates in colour from light yellow to 

 the beautiful orange tint characteristic of this variety. It be- 

 comes permanent about the same time as the colour in the other 

 parts of the body. 



It will be remembefed that the total number of eggs de- 

 posited by the two slugs was 873. From causes which I will 

 presently explain a large quantity of them were unproductive. 

 It is worthy of notice that nearly the whole of the young slugs 

 were similar in colour to the darkest of the parents, only about 

 nine per cent. V^eing coloured similarly to the light-yellow one. 



I shall hope at a future date to return to the question of 

 hereditary transmission of colour, and will only mention here 

 that the kind of food or soil seems to exert no influence what- 

 ever on the coloration, for I have frequently taken several 



J.C, vii., Apr. 1893. 



