III-:LMINTHOLOOY HELMINTHES TIIEMATODES. -1-71 



organization, except an opaque portion situate at the 

 cephalic extremity, and another part extending through the 

 body. 



Several Distomata from, the Acalephse have been made 

 known. The Distomum found by Will (Archiv, 1844, 

 Bd. i, p. 343) in the aqueous passages of Beroe rufcscens 

 presented an annulate body, a retractile caudal extremity, 

 and a sessile abdominal acetabulum. Its excretory organ, 

 filled with transparent, round globules, was bifurcate, and 

 sent up the two lateral branches as far as the oral extremity, 

 where they were united at an acute angle ; an organization, 

 which the Reporter has met with also in Distomum ajjpen- 

 diculatum. Another Distomum, of cylindrical figure, and 

 also furnished with a sessile abdominal acetabulum, was 

 found by Philippi (Midler's Archiv, 1843, p. 66, taf. v, fig. 

 11 and 12) in the stomach of a Physophora. The same 

 naturalist noticed a Distomum, differing from the above, in 

 the stomach, and creeping about between the knob-shaped 

 tentacula of Velella spirans. This latter Distomum was from 

 three fourths to one line long, was provided with a very large, 

 shortly pedunculate, abdominal acetabulum, and was pro- 

 longed into a thick, rounded, posterior extremity. 



From Yarrell (A History of British Fishes, vol. ii, 

 London, 1841, p. 468 : vid. the vignette) we learn that as 

 many as twenty specimens of the rare parasite Tristomitm 

 coccineum were found on the outer surface of the head of an 

 Orthagoriscus mola, taken on the English coast. 



According to J. C. B. Bellamy (Annals Nat. Hist, xiii, 

 1844, p. 78), this discovery has since been repeated on the 

 coast of England. Rathke (Nova Acta Acad. Leopold. 

 Carol. Nat. Curios, torn, xx, p. 1, 1843, p. 238) has very 

 correctly shown that Hirudo hippoglossi or Phylline hippo- 

 ylossi, Ok., can in nowise be referred to Tristomum elon- 

 yatum, Nitzsch, as it has been by Diesing, but must 

 constitute an independent genus and species, differing as it 

 does essentially from Tristonmm donyatum, in the presence 

 of four horny booklets on the but slightly concave surface 



