ENTOZOA. 187 



Octobothrium LEUCK. (Mazocraes HERM., Octostoma KUHN). 

 Body soft, elongate, depressed, furnished posteriorly on each side 

 with four bivalve acetabula. Mouth anterior, simple. (Mostly two 

 anterior acetabula lateral, small.) 



Comp. HERMANN Naturforscher xvn. 1782, pp. 180 182, Tab. iv. 

 figs. ^ ! LEUCKART Breves animal. Descr. Heidelb. 1828, p. 18, ZooL 

 Bruchstuclce in. 1842, pp. 18 33, KUHN Description d'un nouveau genre 

 de I'ordre des Douves, Mem. du Museum xvni. 1829, pp. 357 362. PI. 1 7 bis. 



These species live on the gills of fishes. The most common is the species 

 that lives on the shad (Clupea alosa~L.} : Octobothrium lanceolatum LEUCK., 

 Breves anim. Descr. Tab. i, fig. 7 a, b, KUHN Mem. du Mus. 1. 1. figs, i 3, 

 MATER Beitr. zur Anat. der Entoz. pp. 19 25, Tab. in. figs. i. x. 



Diplozoon NORDM. Body cruciate, as though formed of two 

 worms adhering together. Posteriorly four prehensile organs (suc- 

 torial acetabula) adhere to each limb on both sides, set upon a 

 common disc. 



Sp. Diplozoon paradoxum NORDM. MiTcrogr. Beit. i. Tab. v. vi. (and Ann. 

 des Sc. not. Tom. xxx. PI. 20). This singular animal was discovered by 

 NORDMANN on the gills of the Bream (Cyprinus brama) ; it is 3 5 lines 

 long, and presents a body as if two specimens of Octobothrium had grown 

 together in the middle, like the Siamese twins. Other observers also have 

 met with this animal on the gills of other species of the genus Cyprinus. 

 DUJARDIN found very small entozoa on the gills which resembled a half 

 Diplozoon, and formed thereof the genus Diporpa; he leaves it undeter- 

 mined whether they are young and separate individuals of Diplozoon. 

 [This question has been determined in the affirmative by V. SIEBOLD. He 

 discovered in the middle of the posterior portion of the body two slender 

 booklets which had been overlooked by DUJARDIN in Diporpa and by 

 NORDMANN in Diplozoon : they are bent back at an acute angle. Diporpa 

 is without sex, and always much smaller than Diplozoon; it has, moreover, 

 behind the middle of the body, at that part where the two bodies of 

 Diplozoon coalesce, a sucker. The prehensile organs are much simpler in 

 Diporpa than in Diplozoon; but SIEBOLD found instances of every inter- 

 mediate stage of complexity in them in different pairs of Diporpa which 

 had coalesced, so that in some the resemblance to Diplozoon was in all 

 respects exact. After this conjugation or copulation, the generative organs 

 appear in the united individuals, and eggs are produced. See C. TH. V. 

 SIEBOLD Ueber die Conjugation des Diplozoon paradoxum, nebst Bemerlcungen 

 ueber die Conjugations- Process der Protozoen. In Zeitsch. fur Wissenscli. 

 Zoologie, in. 1851, pp. 6268.] 



The motion of fluid which NORDMANN thought he perceived in the 

 vessels and their branches (in each half of the animal there are on each side 

 two principal stems) is according to later investigations to be ascribed to 

 vibratile cilia which exist on the inner surface of these vessels and produce 

 the appearance of a very rapid current. (EHRENBERG, WIEGMANN'S 

 Archiv. 1835, n. s. 128, MAYER Beitr. z. Anat. der Entoz. s. 23, 24. 





