ScHAEFF — On the Slugs of Ireland. 543 



To show that this mucus has nothing to do with the real colour of the slug 

 one need only wrap it up in a piece of blotting paper, and roll it about for a 

 momeat, when all the mucus will be soaked up. The slug then appears in his 

 natural costume, which is composed of white and a bluish-gray, without any trace 

 of a yellow or red pigment in the skin. 



If we subject the two varieties (Plate LVL, figs. 18 and 19) to the same treat- 

 ment we get a very different result. The first (fig. 18), which, by the way, is not 

 the A. brunneus mentioned by Lehmann (20) and Simroth (38), has no lateral bands, 

 but is rather darker on the back than at the sides. It is a yellow slug, but on the 

 mantle we again find the peculiar reddish mucus, and if the latter is soaked up by 

 blotting paper, we have an entirely yellow slug, and the yellow is due to a 

 pigment investing the skin in small granules. Moreover, the space between the 

 wrinkles is of a bluish colour. The second variety (fig. 19) is entirely yellow, 

 with a lateral band on the back. The margin of the foot in both these varieties 

 is yellow, the yellow colour extending also to one-third the breadth of the foot on 

 each side. 



I found the typical form of A, subfuscus generally between 40 and 45 mm. in 

 length, whilst adults of the first variety were as a rule rather smaller, viz. 35 to 

 40 mm. Of the second variety I obtained only one specimen, whose reproductive 

 organs, although not fully developed, showed that it was more nearly allied to A. 

 subfuscus than to A. ater. Recent investigations into the anatomy of the Arionidce 

 such as those of Pollonera (33) and Simroth (40) may throw light on the affinities 

 of this species, which for the present I must regard as a variety of A. subfuscus 

 more material is available. My specimen was 55 mm. in length. 



The wrinkles in all these slugs differ from those in A. ater in being much 

 shorter, which is especially well seen in the wrinkles just behind the mantle. 

 They are much flatter than those in A. ater, although one has to guard against 

 the influences of temperature in comparing these in different slugs, as I have had 

 occasion to point out under the heading of A. ater. The slime is abundant and 

 clear, and must be distinguished from the intensely yellow mucus which is 

 until produced by the mucus glands on the back and mantle of the slug. 



Anatomy (Plate LVII., fig. 33). — The internal organization of this species differs 

 little from that in A. ater, but all the different parts, of course, are smaller. The 

 ovisperm-duct {ps.) is shorter in proportion than in A. ater. As in the latter there 

 is no penis, the sperm-duct {sp.) ending in a " Patronenstrecke " [pat.) in which 

 the spermatophores are produced. This portion opens into the lower part of the 

 duct of the receptaculum {rec.\ which, in its turn, opens directly into a lower 

 glandular vestibule {Iv.), the upper vestibule being absent. The genital retractor 

 muscle [rm.) is attached to the oviduct (pv.) much higher up than in A. ater (see 

 fig. 32). 



