MOLLUSC A— GENITAL ORGANS 



235 



This ajiparatus, in Limna'a, consists of a large evaginable terminal widening, into 

 which the vas deferens projects in the form of a papilla. Blood pressure causes the 

 penis sheath or prreputinm to be evaginated through the genital aperture, into which 



Fig. 191 



/^'^ 'S, Art ^- 



1U '^ 



Fig. 191.— Genital organs of Limnaea stagnalis (after Baudelot). 1, Male genital aperture ; 

 2, larger penis tube (penis shoatli) ; 3, jirotractors ; 4, smaller penis tube ; 5, vas deferens ; 6, pro- 

 stata ; 7, flattened widening of the vas deferens ; 8, lierniaplirodite duct ; 9, hennaphrodite gland ; 

 10, part of the digestive gland (liver) ; 11, albuminous gland ; 12, nidamental gland ; 13, uterus ; 

 14, pear-shaped body ; 15, receptaculum seminis ; 16, vagina ; 17, female genital aperture. 



Fig. 192.— Genital organs of Oncidium celticum (combined from the figures of Joyeux- 

 Laffuie), somewhat diagrammatic ; only part of the vas deferens is drawn. 1, Male genital aperture ; 

 2, penis sheath (prseputium) ; 3, penis papilla ; 4, vas deferens ; 5, uterus, the seminal fuiTOW in 

 the uterus is indicated by dotted lines ; 6, csecum of the uterus ; 7, oviduct and vagina ; S, ca;cal 

 appendage; 9, receptaculum seminis ; 10, female genital aperture ; 11, albuminous glands; 12, caecum 

 of the hermaphrodite duct, 13 ; 14, hermaphrodite gland. 



it is again withdrawn by means of a retractor. In other species of Oncidium, the 

 copulatory apparatus is complicated by the occurrence of acees.sory penis glands and 

 variously-shaped cartilaginous armature. 



