BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 27. AFD. IV. X:0 G. 7 



The genital basis. 



In Mesothuria intestinalis the eflPerent duct of the geni- 

 tal organ at first takes its way from the external pore in a 

 downward direction close beMnd the madreporic canal and 

 almost parallel to it (Pl. I, fig. 1 — 5). Attached to the dor- 

 sal mesentery, it then deviates from that canal, and runs 

 almost straight backwards slightly above, and in a direction 

 convergent to the rather important genital lacunar cord to 



ll|||WiWl, 



T 



9» 



'""^iflnllli 



The reproductive organ of an individual, 40 mm. long. g eflerent duct; gh 



genital basis; t young genital tubes: åm dorsal mesentery; s madreporic canal; 



h lacunar cord; x germinal cord. Highly magnified. 



which it is attached by two mesenteric membranes bounding 

 the genital sinus of Semper. At their entrance into the geni- 

 tal basis, the efferent duct and the lacunar cord almost meet 

 each other. The lacunar cord, in its turn, is strengthened by 

 means of two membranes connecting it to the alimentary ca- 

 nal and forming the »Nebenschlundsinus» of Semper. 



The genital duct opens into a rather spacious cavity 

 situated within the genital basis and bounded by thick walls 

 of a stroma of fibrous and lacunar structure. The cavity is 

 lined with a ciliated epithelium and is in open communica- 



