new and litth-known Tremntodes. 521 



tlie occurrence is more likely to be the result of chance. 

 There is no doubt, however, that the Miracidia arc set tree 

 before the ova leave the host, as occurs in some other forms, 

 e. g. Distomum macro.ftoinum and D. lanceoJatum *. 



The 8>st(Mnatic position of this species is dilHciilt to decide. 

 It ceitaiiily cannot be chissod in ihe genus Echinostomum, 

 for, although it has a circnni-oral collar, bearing spines, the 

 shape of the collar and the arrangement of the spines on it 

 are quite uidike any found in that genus. Moreover, it 

 diflers widely in internal structure. The most important 

 features of difteronce are : (1) the apposition of the pharynx 

 to the oral sucker and the absi-nce of oesophagus, (2) the 

 position of the testes, (3) tlut situation and extent of the 

 vitelline glands, (-i) the advanced development of the ova. 

 These features are of generic importance. For the same 

 reasons it cannot be included with any of the allied genera 

 Stcj'hmioslomum, Aca7ithostomum,Cent/'ocestus, and Ascocotyle^ 

 eacli of which possesses a crown of spines round tiie mouth. 

 In its internal anatomy it a))|)roximates more closely to the 

 genus Pygorchis^ Looss f, but in s])ite of certain similarities 

 the points in which it differs are of sufficient importance to 

 prevent its inchision in that genus. It bears the closest 

 resemblance of all to an as yet unique species, Distomum 

 piiUtciani, Braun %• Together they agree with Fygorchis in 

 havin": the intestinal diverticula extending almost to the 

 posterior extremity of the body, the vitelline glands of s:nall 

 extent and entirely behind the ventral sucker, and in the 

 presence of well-developed eye-spots within the ova. Pyg- 

 orchis, however, differs in having the testes placed obliquely 

 behind each otiier, in having the vitelline glands stretching 

 oljliquely across the body, in the forward position of the 

 genital a])erture, and in the possession of a jicnis-sac. In 

 addition, Pyijorchis is destitute of spines of any description. 

 Distominn pittacium also entirely lacks spines, and in Braun's 

 figure there is not the slightest vestige of a collar round the 

 oral sucker. The otherwise remarkable resemblance between 

 this species and Zeuyorchis acanthus inclin(.'S one to doubt 

 whether Braun's species was really provided with spines or 

 not. Judging from the tenacious manner in which the 

 spines remain fixed to the body in my examples, it seems 

 very unlikely that they can have been completely strippetl 

 off; besides, in any case, the collar would remain. 



The question now is whether Distoinuin pittacium is to be 



* Bronn's ' Thierreich,' Vermes, I. i. p. 778. 

 t Zool. Jahrbiicher, 8yst. xii. p. ob7. 

 i Op. cit. -\vi. p. 140. 



