The human transport of animals across the Northern Atlantic 201 



higher viability in comparison with related bisexual forms and species (Lindroth, 

 1954 e). The aspect of parthenogenesis in the first place applies to Curculionids 

 (Weevils; below, p. 210). Concerning the Staphylinid Amischa analis Gr., vide 

 Strand (1951). In some Iso-Myriapods, too, a more or less constantly partheno- 

 genetic reproduction has largely contributed towards the wide passive dispersal 

 (mainly with man) of these species. In the Newfoundland fauna this applies to 

 the Chilopod Lamyctes fulvicornis Mein. (Palmen, 1954, p. 144), the Diplopod 

 Proteroiulus fuscus a. St. (Palmen, 1952, p. 17), and the Oniscoid Trichoniscus 

 pusillus pusillus Brandt (Palmen, 195 1, p. 2). 



Another animal, the extremely rapid dispersal of which may be attributed at 

 least in part to parthenogenesis, is the euryhaline Mollusc Hydrobia (Potamopyrgus) 

 jenkinsi Smith {vide Bondesen & Kaiser, 1950). Its original home is unknown but 

 it may have been carried to NW. Europe by human transport from America. The 

 Lumbricid worms Allolobophora caliginosaSav., Bimastus tenuis Eis., Dendrobaena 

 subrubicunda Eis., Eisenia rosea Sav.,and Eisetiiella tetraedra Sav., almost cosmopoli- 

 tan in distribution and evidently introduced into North America from Europe, are 

 likewise parthenogenetic, at least in part (Gavrilov, 1935, 1940; Muldal, 1952; 

 Omodeo, 1952, p. 246), and this may also apply to the rest of peregrine 

 Oligochaeta. 



Functionally similar are hermaphroditic species capable of self-fertilization. 

 Possible examples among terrestrial (and, in part, limnic) animals are to be found 

 among Mollusca and Oligochaeta. Of the species dealt with in this book, Arion 

 ater L. (Kiinkel, 1916, p. 409 a.f.; Perrot, 1939) and several species of Lymnaea 

 (Hubendick, 195 1, p. 32) are considered capable of self-fertilization^ and the same 

 has been supposed with respect to the form of Deroceras laeve Miill. with reduced 

 penis (Boettger, 1932, p. 402; Meeuse & Hubert, 1949, p. 25), as well as for 

 members of the following families (in part even the same species), which have 

 crossed the North Atlantic by human agencies: Arionidae, Helicidae, Limacidae, 

 Physidae, Planorbidae, and Zonitidae {vide bibliography in Larambergue, 1939, 

 p. 41-43). The occurrence of self-fertilization in Oligochaeta has been suggested in 

 those cases, in which reproduction was observed in isolated individuals, as in 

 Dendrobaena octaedra Sav. and Eisenia foetida Sav., both of world-wide distribu- 

 tion, but parthenogenesis, as in the species mentioned above, seems equally 

 probable. 



^ It must be regarded as very difficult to separate, conclusively, selflFertilization from 

 parthenogenesis in hermaphroditic animals without cytological investigation. 



