ENTOZOA. 



83 



37 



white colour, and terminate bj two trunks in a common canal, which 

 ends at the base of the receptaculum penis. This appendage is 

 spirally disposed when flaccid, is tubular, and distinctly perforated at 

 the apex. 



The ovaria occupy the whole margin of the body for a line in 

 breadth : they consist of minute, branched tubes, in which the ova 

 are developed, as in acini. The oviducts are close to the ventral 

 integument, and terminate in a single large uterine canal, which is 

 disposed in many convolutions between the subventral acetabulum 

 and the bursa penis: it terminates by a vulva, or distinct pore, 

 immediately behind the male bursa. The ovarian ova are colourless 

 and pellucid, but become opaque as they approach the oviduct : 

 having entered this tube they acquire a white glistening tunic, and 

 afterw^ards a yellow colour, which becomes deeper as they approach 

 the vulva. 



The Distoma lanceolatum {fig. 37.) has been regarded as the young 

 of the Distoma hepaticum ; but it is of a dilFerent 

 form, has a different anatomical structure, particularly 

 as regards the alimentary canal, and its title to rank 

 as a distinct species is sufficiently vindicated by its 

 power of developing fertile ova without changing its 

 characteristic shape or increasing in size. It rarely 

 equals five lines in length, but is more commonly three 

 lines long ; flat, lanceolate, more attenuated anteriorly, 

 and with an obtuse caudal apex. 



The suctorial pores are relatively larger than in the 

 D. hepaticum. The anterior sucker («) looks down- 

 wards, and is perforated in the centre by the mouth : 

 the genital pores are half way between this and the 

 hinder sucker (Z>). The transparency of the integu- 

 ment allows the internal parts to be readily discerned. 

 The alimentary canal, commencing by a kind of 

 pharynx, is continued as a very slender tube (c) to 

 the bursa penis, where it bifurcates, each division (c?) 

 being continued without further ramification along the 

 right and left sides of the body to the tail, where it 

 ends in a blind extremity. The minuter excretory 

 system of vessels has not been discerned in this small Distoma. The 

 simplicity of its digestive apparatus makes the analogy very close 

 between the D. lanceolatum and the Tcenice. 



In the interspace of the two digestive tubes four opake whitish 

 spots are visible, of which the three anterior or larger ones {e) form 

 the testes. Each transmits from its anterior margin a very minute 



G 2 



i 



Dist. lanceolatum, 

 magiiihed. 



