50 HARLEY N. GOULD 



when the oogonial cells, after a period of division, develop into 

 oocytes and enter upon the growth period. 



The goniduct serves for the transference of both spermatozoa 

 and eggs, but is, structurally, entirely different in the male and 

 the female phases. In the male phase it is differentiated into 

 seminal vesicle and vas deferens. 



The accessory male organs appear only when the testis de- 

 velops. In the 'sexually inactive' animals there is no penis, 

 seminal vesicle nor sperm groove. These develop very quickly, 

 however, when male differentiation takes place in the gonad. 



During the change from the male to the female condition or 

 upon the premature loss of the male condition, the penis, seminal 

 vesicle and sperm groove degenerate. Before its degeneration 

 the seminal vesicle absorbs the contained spermatozoa into its 

 wall, where they dissolve. 



As the female phase is gradually assumed, the goniduct 

 greatly increases in size, acquires longitudinal folds and glands 

 in its wall, and becomes the oviduct. At this point in the life 

 history the ' gonopericardial duct' is also developed, connecting 

 the pericardial chamber with the oviduct. 



BIBLIOGRAPHY 



Ancel, p. 1903 Histog^nese et structure de la glande hermaphrodite d'Helix 



pomatia. Arch. Biol., T. 19, pp. 389-652. 

 DE Bruyne, C. 1903 Contribution a I'etude de la cellule foUiculaire des 



glandes genitales des Gastropods. Bull. Acad. Beige. 

 V. Brtjnn, M. 1884 a Untersuchungen iiber die doppelte Form der Samen- 



korper von Paludina vivipara. Arch. f. Mik. Anat., Bd. 23. 



1884 b Weitere Funde von zweierlei Samenkorper in demselben Tier. 



Zool. Anz., Bd. 7. 

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Hermaphroditismus. Beobachtungen an Rhabditis nigrovenosa. 



Verh. Phys. Med. Ges. Wiirzburg, Bd. 41. 

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1. Die Differenzierung der Keimzellen bei Helix arbustorum. Arch. 



f. Zellfsch., Bd. 7, Heft. 3, s. 314-343. 

 CoNKLiN, E. G. 1897 The embryology of Crepidula. Jour. Morph., vol. 13, 



no. 1, pp. 1-226. 



1898 Environmental and sexual dimorphism in Crepidula. Proc. 



Acad. Nat. Sci. Phila., 1898, pp. 435-444. 



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1902. 



