DESCRIPTION OF THE PLATES. 125 



there has been a great want of proper figures or 

 descriptions of the true generic and specific 

 characters of these animals, a point of the 

 utmost importance for the obtaining of a proper 

 knowledge of them : with this view the Author 

 has paid scrupulous attention to the leading 

 characters, and these he has placed in the 

 form of a synopsis at the end of the Chap- 

 ter. All the drawings have been made with 

 the view of illustrating these characters more 

 fully. The disposition of the teeth, and their 

 forms, are perhaps the most certain external 

 characters. 



PLATE VIII. Fig. 4. Magnified view of a small portion of the external 

 or tubular membrane of Diskostoma acephalocystis. 



a Larger disc. 



b Smaller one on its surface. 



c Tubuli. 



d Extremities of tubes. 

 e e Gemmules, which at this stage of developement 



may act as absorbents. 



Fig. 5. Natural size of Diskostoma acephalocystis. 

 Fig. 6. Diskostoma acephalocystis in various stages of 



developement. 



a a a Small cells arising from the attached surface of 

 the tubular membrane. This is the manner in 

 which the original group increases in size. 



b More advanced. 



c First stage of second mode of developement, or 

 that for the extending of the parasite to as yet 

 uninfested parts of the body, for the purpose of 

 forming new groups. 



d Second stage. 



e Third stage. 



/ Root where the original germ became fixed. 



g External or tubular membrane. 



Fig. 10. Section of Astoma acephalocystis, showing its in- 

 ternal structure. 



PLATE IX. Fig. 1. Portion of sac of cysticercus, much magnified. 

 a a Absorbing cells of absorbing membrane. 



