MEMOIRS 



READ BEFORE THE BOSTON SOCIETY OF NATURAL HISTORY. 



i. ox dlstomum ceassicolle rud. ; with beief notes on huxley's proposed 



Classification of Woeiis. 



By Charles Sedgwick Minot. 



Read Feb. 21, 1877. 



J. HAVE recently 1 attempted to prove in detail that the Nernertines cannot be retained 

 among the Plathehninths, and that the remaining forms of the class must be grouped 

 differently from the hitherto accepted manner. One of the principal changes was the union 

 of the Trematods and Cestods in one division under the name of the Vaginiferas. The 

 following paper has been prepared with a view to justify the proposed change, by a com- 

 parative investigation of a fluke and a tape worm. I have chosen Distomum crassicolle on 

 the one hand, and Caryo-pliylhms on the other, as representative species. I have already 

 prepared sections of the latter, but am obliged for personal reasons to postpone the detailed 

 investigation of them ; and it appears to me desirable, therefore, to publish my observations 

 on Distomum at once. 



I prepared in July, 1876, while in Leipzig, three series of sections, and mounted two 

 specimens in Canada balsam. All of these preparations were stained with carmine. Each 

 of the three series comprised a whole individual from beginning to end, and without a 

 break ; the sections were made with the aid of a sledge microtome. 2 Two of the series 

 were of transverse, one of longitudinal sections ; nevertheless there were parts of the 

 animal which could not be well seen in any of the preparations. I must therefore apologize 

 for the incompleteness of the following description, although unavoidable, because I cannot 

 at present obtain any more specimens of this species. 



Distomum crassicolle measures about 4 mm - in length, and 1.2 mm in width, and its 

 dorso-ventral diameter is about 1 - 0.9 mm - Its oral sucker is small, fig. 1, M, although 

 somewhat larger than the ventral one, S, which is placed on the ventral median line, near 



1 Minot. On the Classification of some of the lower Arbeiten des Zoot.-zool. Inst. Wiirzburg. Bd. Ill, p. 405. 



Worms. Proc. Boston Soc. Nat. Hist., Vol. xix, p. 17. 1877. 



Minot. Zur Anatomie der Turbellarien, zugleich ein 2 A description of this invaluable instrument may be 



Beitrag zur Classification der Platthelmintben. Semper's found in the American Naturalist for April, 1877. 



MEMOIKS BOST. SOC. SAT. HIST. VOL. III. 1 



