CASTLE. — META3IERISM 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 Hirudinea 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 lensthenius of individual somites. Lenaftheninsr of the individual 

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

 number of rings in a somite. 



Papers Cited. 

 Apathy. S. 



88. Analyse der jiusseren Korperforiii der Hirudiueen. Mitth. Zool. Sta. 

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

 Blanchard, R. 



"94. Hirudiuees de I'ltalie coutiueutale et insulaire. Boll. Mus. Zool. e 

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

 Bristol, C. L. 



'99. Tlie Metamerism of Nephelis. Jour, of Morph. Vol. 15, pp. 17-72. 

 PI. 4-8. 

 Gratiolet, P. 



'62. Recherches sur rorganisatiou du systeme vasculaire dans la sangsue 

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

 PI. 7. 

 Moore, J. P. 



'95. The Anatomy of Bdellodriliis illurainatus, an American Discodrilid. 

 Jour, of Morph. Vol. 10, pp. 497-540. PI. 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 I'etude anatomique du genre Pontobdelle. Ann. Sci. 

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

 Whitman, CO. 

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

 215-315. PI. 12-15. 

 Whitman, C. O. 

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

 39, 40. 



