636 



enthält der runde Zapfen, auf welchem sie sitzen, markbildende Zellen 

 und Mark. Dieses Mark ist jedoch nicht in continuirlicher Verbindung 

 mit dem Mark der Hornfaser, welcher das Büschel aufsitzt, sondern 

 durch die Rindenschichten der alten Faser davon getrennt. Ausge- 

 wachsene Zweige zeigen aber stets einen continuirlichen Zusammen- 

 hang ihres Markes mit dem Mark des Stammes, was ein secundäres 

 Durchbrechen der Rindenschichten der Stammfaser beweist. Ich habe 

 auch einige Fasern beobachtet, bei denen dieses Durchbrechen eben 

 stattfand, und sah dann deutlich. Avie von der Kuppel der markbilden- 

 den Zellen aus ein Fortsatz gegen die Ursprungsstelle der Zweigfaser 

 hin wucherte. 



3. A new Species of Branchiobdella. 



by Prof. C. O. Whitman. 



Hitherto only two species of Branchiohdella have been distin- 

 guished on Astacus ßuviatilis^ namely, B. astaci Oàìex and B. parasita 

 Henle. An examination of specimens obtained from the River Cray- 

 fish of Leipsic for purposes of comparison with species found in Japan 

 has shown that A. ßumatilis agrees with A. Japonicus in bearing three 

 distinct species of Branchiohdella. Although the Japanese species will 

 be described elsewhere, I may here mention that there is a correspon- 

 dence in size as well as in number between them and the European 

 species, there being one comparatively long (10 — 15 mm) and two short 

 species (2 — 4 mm) in each case. 



In each of the Japanese species the two lips (dorsal and ventral) 

 are tentaculiferous, while in the continental species the lips are entire 

 in the new species, very faintly two-lobed in B. astaci., and more or 

 less distinctly four-lobed in B. parasita i. 



The jaws have a characteristic form and size for each species ; and 

 the number of denticles forms an important diagnostic character. The 

 denticles are more numerous in the Japanese species than in the Euro- 

 pean. In B. parasita there are seven denticles (I large median and 3 

 small lateral on each side) ; in B. astaci., six (2 large lateral and 4 small 

 intermediate). The new species has five denticles on each jaw (1 large 

 median, 1 somewhat smaller lateral and 1 still smaller intermediate on 

 each side, and may therefore be called B. pentadonta. The jaws, 

 viewed from above or below, are triangular in B. parasita, and sub- 

 crescentic in B. astaci. 



1 These lobes are not mentioned by D orner, Zeitschr. f. wiss. Zool., B. XV, 

 p. 464. 



