310 LEIDY'S DESCRIPTIONS OF DISTOMA. 



REFERENCES TO PLATE XLIII. 



The figures are all highly magnified. 



Fig. 1. Distoma horridum : a. ventral acetabulum with the mouth dilated ; 6, pharynx; c. oesophageal 

 bulb; rf. oesophagus ; e. intestinal rami; /. ovaries; g. oviduct, containing numerous ova; A. vagina ; 

 i. testes ; k. vaginal or basial portion of the penis ; I. penis ; m. ventral acetabulum, vi^ith the appearance of 

 a transverse fissure or orifice in its centre. 



Figs. 2 to 16 inclusive, Distoma vagans. 



Fig. 2. D. vagans in the second stage, a. oral acetabulum, with the two oral orifices represented, the 

 external triangular, the internal 'transversely elliptical ; 6. pharynx ; c. oesophageal bulb ; d. oesophagus ; 

 e. intestinal rami ; /. contractile sac communicating with the exterior and the vascular canals; g. vascular 

 canals ; h. ventral acetabulum, with its elliptical orifice represented ; i. male generative aperture. 



Fig. 3. Oral acetabulum with the orifices contracted or closed. 



Fig. 4. Oral acetabulum with the oral orifices dilated ; the exterior triangular, the interior circular. 



Fig. 5. The ventral acetabulum, with its orifice dilated. Three corpuscles are exhibited which were 

 moved to and fro in the contraction and expansion of the organ. 



Fis. 6. The globular form of the oral acetabulum. 



Fig. 7. The posterior contractile sac closed or contracted to its utmost degree. 



Figs. 3 to 7 inclusive were drawn from the animal in the second stage. 



Fig. 8. Circulation, or vascular system of the third stage, a. to b. the vessel which is supplied on its 

 inner surface with vibrillce. 



Fig. 9. Posterior contractile sac, and partly detached tail, from the animal in the second stage. 



Fio-. 10. Commencement of the vessel furnished with vibrillcE, from the third stage, representing the 

 revolution of a molecule through the agency of the vibratory action. 



Fif. 11. Appearances produced by the decreasing rapidity of the vibratory movement in fragments of 

 the vessel furnished with vibrillae. The progressive decrease is represented in the course a, d. b, c. 



Fig. 12. Represents the mode of contraction in different directions of the sarcous cells beneath the 

 epidermis. 



Fig. 13. D. vagans in the first stage : a. oral acetabulum ; b. pharynx ; c. oesophageal bulb ; d. oesophagus; 

 e. intestinal rami ; /. caudal appendage ; g. blood vessels ; h. ventral acetabulum ; i. organic nucleated cells 

 among the contents of the intestinal rami. 



Fie. 14(. Outlines of the forms into which D. vagans will change itself in the second stage of its exist- 

 ence. 



Fie. 15. Vesicular or general parenchymatous structure of the body. 



Fig. 16. Granular, globular, and spicular contents of the intestinal rami of the first stage. 



