CASTLE. — METAMERISM OF THE HIRUDINEA. 303 



also in the abbreviated somites of Glossiphonia, as a stage intermediate 

 between the three-ringed and one-ringed conditions of the somite. 



10. The phenomenon of ring multiplication in the Ilirudinea is 

 correlated with the restricted number of somites found in the body. 

 Increase in the number of somites does not take place in the body of 

 the adult leech. Without this, elongation of the body is possible only 

 through lengthening of individual somites. Lengthening of the individual 

 somite has probably been the cause, phylogeiietically, of increase in the 

 number of rings in a somite. 



Papers Cited. 



Apathy, S. 



88. Analyse dor ausseren Korperform der Iliruduieen. Mitth. Zool. Sta. 

 Neapel. Bd. 8, pp. 153-232. Taf. 8, 9. 

 Blanchard, R. 



'94. Ilinulinees de l'ltalie continentale et insulaire. Boll. Mus. Zool. e 

 Anat. comp. Torino. Vol. 9, No. 192, pp. 1-81. 30 Fig. 

 Bristol, C. L. 



'99. The Metamerism of Nephclis. Jour, of Morph. Vol. 15, pp. 17-72. 

 PI. 4-8. 

 Gratiolet, P. 

 '62. Recherches sur I'orgauisation du systeme vasculaire dans la sangsue 

 medicinale et l'Austome vorace. Ann. Sci. Nat., Zool. T. 17, pp. 175-225, 

 PL 7. 

 Moore, J. P. 



'95. The Anatomy of Bdellodrilus illuminatus, an American Discodrilid. 

 Jour, of Morph. * Vol. 10, pp. 497-540. PL 28-32. 

 Oka, A 



'94. Beitrage zur Anatomic der Clepsine. Zeit. f. wiss. Zool. Bd. 58, pp. 

 79-151. Taf. 4-6. 

 Vaillant, L. 



'70. Contribution a l'etude anatomique du genre Pontobdelle. Anu. Sci. 

 Nat., Zool. T. 13, pp. 31-71. PL 8-10. 

 Whitman, C. O. 

 '78. The Embryology of Clepsine. Quart. Jour. Micr. Sci. Vol. 18, pp. 

 215-315. PL 12-15. 

 "Whitman, C. O. 

 '92. The Metamerism of Clepsine. Festschr. Leuckarts. pp. 385-395. PI. 

 39, 40. 



