142 



HELMINTHOZOA. 



(371.) Through the walls of the ventral surface of the body two 

 nervous filaments (c) are discoverable, which, crossing over the root of 

 the anterior sucker oracetabulum,and gra- 

 dually diverging, may be observed to run 

 in a serpentine course towards the caudal 

 extremity, where they are lost : it would 

 even seem that on either side of the oeso- 

 phagus there is a very slight ganglion, 

 from which other nervous filaments arise 

 to supply the suckers and the anterior 

 part of the body. 



(372.) The organs of generation in the 

 fluke are very voluminous, occupying, 

 with the ramifications of the alimentary 

 tubes, the whole of the interior of the 

 animal : in the diagram they are not re- 

 presented on the right side, in order that 

 the distribution of the intestine may be 

 better seen ; and on the left side the ali- 

 mentary vessels are omitted, to allow the 

 general arrangement of the sexual system 

 to be more clearly intelligible. 



(373.) These animals are completely 

 hermaphrodite, not only possessing di- 

 stinct ovigerous and seminiferous canals, 

 which open separately at the surface of 

 the body, but even provided with external 

 organs of impregnation, so that most probably the cooperation of two 

 individuals is requisite for mutual fecundity. 



(374.) To commence with the female generative system, we find the 

 ovaria (Ji) occupying the whole circumference of the body. When 

 distended with ova, the ovigerous organ is of a yellow colour ; and 

 when attentively examined under the microscope, it is seen to be made 

 up of delicate branches of vesicles united by minute filaments, so as to 

 have a racemose appearance. From these clusters of ova arise the ovi- 

 gerous canals, which, uniting on each side of the body into two principal 

 trunks, discharge their contents into the large oviducts (g). The ovi- 

 ducts terminate in a capacious receptacle (e), usually called the uterus ; 

 and from this a slender and convoluted tube leads to the external orifice, 

 into which a hair (d) has been inserted. On each side of the uterus we 

 find a large ramified organ, made up of c&cal tubes (/), which opens into 

 the uterine cavity, and no doubt furnishes some accessory secretion 

 needful for the completion of the ova. 



(375.) The male apparatus occupies the centre of the body. The 

 testes (k), in which the spermatic fluid is secreted, consist of convoluted 



Anatomy f Distoma. a, anterior 

 sucker and oral orifice ; 6, alimentary 

 canal ; c, nervous system ; d, external 

 opening of female generative appa- 

 ratus ; e, uterine receptacle ; f, acces- 

 sory appendage to ditto ; g, oviduct ; 

 li, ovary ; i, common canal, receiving k, 

 convolutions of testis; I, vas deferens; 

 m, capsule of the penis; w,intromittent 

 organ. 



