108 



ENTOZOA. 



the numerical strength of the flukes and roundworms. Upwards 

 of two hundred and fifty distinct forms have been described, but 

 it may be doubted if two hundred of these are really good species. 

 Assuming the latter to represent their number, the following 

 simple table of classification will conveniently embrace all the 

 species : — 



C Tceniadce (Family I.) 

 Cestoda \ Bothriocephalidce (Family II.) 

 (. Tetrarhynchid^ (Family III.) 



i 



Fia. 24. — Head of Taenia paeadoxa, Rudolphi ; fi'om the intestine of an oyster-catcher (Hcema- 

 topus ostrealegus, L.) ; a, with the rostellum partly invaginated ; b, end of the rostellum 

 expanded ; X 260 diam. — Original. 



TcBniadce. — The true tapeworms are characterised by the pos- 

 session of a small distinct head furnished with four simple oval 

 or round suctorial disks (suckers), and commonly also with a more 

 or less strongly-pronounced rostellum (proboscis) placed at the 



