42 PAUL PELSENEER. 



20. Milne-Edwards. — "Observations sur divers Mollusques," * Ann. d. Sci. 



nat.,* ser. 2, t. xviii, pi. x, fig. 1. 

 20a. Humbert. — "Note sur la structure des organes geaitaux de quelques 

 especes du genre Pecten," ' Ann. d. Sci. nat.,' ser. 3, t. xx, p. 338. 



21. Lacaze-Duthiers. — Loc. cit., p. 208. 



22. FuLLARTON. — " Ou the Development of the Commou Scallop," * Eighth 



Ann. Rep. Fish. Board for Scotland,' p. 290, pi. viii. 



23. Jackson. — "Phjlogeuy of the Pelecypoda," 'Mem. Boston Soc. Nat. 



Hist.,' vol. iv, pp. 341, 348. 

 23a. Humbert. — Loc. cit., p. 338. 



24. VON SiEBOLD.— ' Arch. f. Anat. u. Phys.,' 1837, p. 383. 



25. Leydig. — "UeberCjclas cornea. Lam.," 'Arch. f. Anat. u. Phys.,' 



1855, p. 59. Stefanoff. — "Ueber die Geschlechtsorgane und die 

 Entwickeluug von Cyclas," 'Arch. f. uaturg.,' 1865, p. 3. 



26. Steenstrup. — ' Undersogelser over hermaphroditismens tilvaerelse i 



naturen,' 1845, p. 69. 



27. Ray Lankester. — " Contributions to the Developmental History of the 



MoUusca," ' Phil. Trans.,' 1875, p. 1. 



28. Pelseneer. — "Deux nouveaux Pelecypodes hermaphrodites," ' Comptes 



rendus Acad. Sci. Paris,' t. ex. Pelseneer. — " Sur I'existence d'un 

 groupe entier de Lamellibranches hermaphrodites," ' Zool. Anzeiger,' 

 1891. 



29. F. J. H. Lacaze-Duthiers. — Loc. cit., p. 211. 



30. H. DE Lacaze-Duthiers. — "Morphologic des Acephales," 'Arch. d. 



Zool. Exper.,' ser. 2, t. i, p. 216. 



31. Leuckart. — 'Zoologische Untersuchungen,' Heft iii, p. 76. 



32. Since Eisig (" Beitrage zur Anatomic und Entwickelungsgeschichte der 



Geschlechtsorgane von Lymnaeus," * Zeitschr. f. wiss. Zool.,' Bd. xix, 

 p. 310), &c. According to Babor (" Ueber den Cyclus der Ge- 

 schlechtsentwickelung der Stylommatophoren," ' Verhandl. Deutsch. 

 Zool. Gesellsch.,' 1894, p. 57), Agriolimax Isevis and Limax 

 maximus furnish exceptions and are protogynous. 



33. Pelseneer. — " Recherclies sur divers Opisthobranches," ' M^m. Cour. 



Acad. Belg.,' t. liii, p. 21. 



34. Pelseneer. — Ibid., p. 24. 



35. Leuckart. — Loc. cit. 



36. Chun. — " Bericht iiber cine nach den Canarischen Inseln im Winter, 



1887-8, ausgefiihrte Reise," ' Sitzungsber. k. Akad. d. Wiss. Berlin,' 

 1889, p. 543. 



