36 THÉEL, HERMAPHRODISM IN HOLOTHURIDS. 



Explanation of the plates. 



Plate I. 



Fig. 1. Anterior portion of Mesothuria intestinalis, the right and left 

 body-walls having been cut away in order to show the repro- 

 ductive organ »in toto» on the left side of the dorsal mesen- 

 tery. Magnification Vi- 



» 2. Generative organ from a small individual. a, efferent duct; 

 h, lacunar blood-cord; c, geuital basis; d, genital tubes. 

 Magnification ^jx. 



» 3. Genital basis, a, efferent duct; h, lacunar blood-cord; c, the 

 basis carrying the genital tubes; d, the tubes cut off; e, the 

 porterior naked end of the genital basis with protuberances; 

 y, the foremost minute clusterly tubes. Magnification ^ji. 



» 4. Same as above, though from another individual with the po- 

 sterior end-portion of the genital basis more devcloped. Signi- 

 fication of the letters as in Fig. 3. Magnification ^l\. 



» 5. Same as above, though from an older specimen. Signification 

 of the letters as in Fig. 3. Magnification ^jx. 



» 6. Transverse section of the left wall of the efferent duct. a, 

 the cavities of the germinal cord, stained with Borax-carmine 

 and drown with the Abbé's camera lucida. Highly magnified. 



» 7. Similar section of the same duct taken posteriorly to the 

 former. Highly magnified. 



» 8. Transverse section through the most anterior part of the geni- 

 tal basis of the same individual. a, cavity of the efferent 

 duct; h, genital sinus of Semper; o, opening between the 

 genital sinus and the perivisceral cavity ; /, one of the minute 

 club-shaped genital tubes; .r, the cavity of the germinal cord 

 in open communication with the cavity of the efferent duct; 

 m, dorsal mesentery. The cilia are drawn only where they 

 are distinctly stained with carmine. Drawn with the camera 

 lucida under high magnifying power. 



» 9. Transverse section of an immature female tube. e, eggs; /, 

 folds filled with blood-fluid and leucocytes; fm, follicle 

 membrane. Treated with iron-hsematoxyliue according to 



