1922. No. 5. 



ARIONIDAE OF NORWAY. 



27 



The shape of the atiiiDii [afr.) is a good species character in the adult. 

 It is short and thick, with about the same breadth as length. In the young 

 it is usually ribbon-shaped. 



The spcriuatophoj'c is said to be long and serrate. 



Variation. Like the anatomy (jaw, radula and the reproducti\-e organs) 

 the colour is liable to variation, according to which various authors 

 have described a series of forms, designated as species, varieties, sub-species 

 or sub-\-arietie5. However, the study of a great number of living specimens 

 as well as a revision of the descriptions often prove that several of these 

 forms are connected through all intermediate colours. Consequently the}' do 



Ori'K^ 



Fig. 19. Lower parts of the reproductive 

 organs of Arion sitbfusctts, ^ I. 



atr. atrium genitale, ep. epiphallus, o. ovi- 

 duct, o.-sp.-d. ovispermatoduct, rcc. recep- 

 taculum, retr. retractor, v. d. vaï deferens. 



Fig. 20. Lower parts of the reproductive 

 organs of Arion siib/iisais, ' 1 . 



a/r. atrium genitale, ep. epiphallus, o. ovi- 

 duct, o.-sp.-d. ovispermatoduct, rec. recep- 

 taculum, re/r. retractor, v. d. vas deferens. 



not deserve the names of separate varieties. It should be remembered, 

 that even the same individual passes through changes of colour, and that 

 a brown specimen turns greN'ish when the orange mucus is wiped away. 

 Obviously it is not easy to demonstrate all intermediate colours between 

 the grey and black animals, and it may be granted that several genot\-pes 

 probably conceal themselves between these limits. According to the types 

 of colour the common Norwegian forms belong to the series of "varieties" : 



var. cincrco-fiisca Draparnaud, • — grey. 



var. succinca Bouillet — from 3'ellow to orange. 



var. fiiUginca Morelet — dark brownish. 



var. nigricans Pollonera — black. 



