38 CLASSIFICATION OF THE ANIMAL KINGDOM. 



Treniatode Worms. The possession, however, of a series of rudimentary 

 feet, provided with hooks, is a character which would separate it from the 

 Trematodes, and would rather indicate an alliance with the Chsetopod 

 Annelides. 



(Pagenstecher, Trematoden-larven und Trematoden, Heidelberg, 1857 ; 

 Van Beneden and Hesse, Bdellodes et Trematodes marins, Mem. Acad. de 

 Bruxelles, 1863 and 1865 ; Sommer, Anatomie des Leberegels, Distoma 

 hej)aticum, Zeitschr. fur Wiss. Zool., 1880.) 



Fig. 31. A Trematode Worm (Din- 

 toma lanceokitum), enlarged, aa, An- 

 terior sucker, with the mouth at its 

 bottom ; ap, Posterior sucker ; o, Gul- 

 let, dividing behind into the two 

 branches of the intestine, which are 

 unbranched, and terminate behind 

 in blind extremities (i i); p, External 

 opening of the water-vessels, which 

 divide above so as to cross the blind 

 ends of the intestine. The remain- 

 ing letters refer to the different parts 

 of the reproductive organs. 



rs 



Fig. 32. One of the Turbellarian Worms (Lep- 

 toplana tremellaris), enlarged, o, Mouth ; pr, 

 Proboscis; g. The principal nerve -ganglion, 

 placed in the anterior part of the body, and 

 giving off numerous radiating branches (ri) ; p, 

 Penis ; vd, Vas deferens ; vs, Vesicula seminalis ; 

 am, Opening of male reproductive organs ; t, 

 Teetis ; ov, Ovary ; it, Uterus, partly filled with 

 eggs ; of, Opening of the female reproductive 

 organs ; rs, Eeceptaeulum seminis ; ga, Albumi- 

 niparous gland. 



