1 62 WHITMAN. [Vol. I 



6. The ''Pharyngeal Clefts^ 



In Fig. I, PI. IV., are shown two remarkable grooves just in 

 front of the thickened anterior ends of the germ-bands, marking 

 the line of junction with the cephalic lobe. These groove- 

 like formations are remarkably distinct in C. com.planata, and 

 are found in every species of Clepsine that I have examined. I 

 have before described them as "pharyngeal clefts" (No. i, pp. 

 60—61), but I now have considerable doubt as to the correct- 

 ness of this interpretation. They were not so well marked in C, 

 parasita, and I have not thus far obtained the material necessary 

 for a detailed study of them. 



Salensky (No. 15, p. 25) describes in Branchiobdella what he 

 calls a " bifurcation de la gouttiere medullaire," which corre- 

 sponds nearly in position and appearance with the " pharyngeal 

 clefts " of Clepsine. 



IV. SPECIAL AND GENERAL QUESTIONS. 

 I. Larval Nephridia. 



No larval nephridia have thus far been discovered in the 

 Rhynchobdellidae, and the relations of these organs to the per- 

 manent nephridia in the Gnathobdellidae have not yet been 

 made clear. Bergh was not aware of the existence of distinct 

 nephric cell-strings, and hence his descriptions and figures do 

 not settle the place of origin of the larval nephridia with the 

 precision that could be desired. It would seem from Bergh's 

 statements that these organs are derived from the two " outer 

 strings," i.e.^ the lateral row (?«'), and the adjacent nephridial 

 row in my figures. " An den ausseren Strangen sind als schrag 

 nach aussen und hinten gerichtete Zweige die Anlagen der 

 Urnieren, deren Aulastoma vier Paare besitzt, sichtbar. 

 Die vier Urnierenpaare entstehen somit als seitliche Sprossen 

 von zwei Langsstrangen, welche letztere sich spater mit den er- 

 wahnten inneren Strangen vereinigen " (No. 29, p. 91). As 

 the nature and fate of these " longitudinal strings " remained 



(29.) Bergii, R. S. Thatsachen aus der Entwicklungsgeschichte der Blutegel. 

 Zool. Anz. VII. No. i6o, p. 90. Feb. i8, 1884. 



