34 OF THE PRINCIPAL WORMS 



half an inch in leugth,(68) etc. We perceive that 

 the external form of the young worms thus differs 

 from that of tlie more aged, and that the external 

 appearance of the latter seems quite different from 

 tliat of the taenia when arrived at its full size and' 

 perfect growth. 



This accidental diversity has therefore been 

 very improperly regarded as a characteristic index 

 of particular species, as we have already remark- 

 ed ;(69) and naturalists have fallen into a great er- 

 ror, especially those, who, blinded by the authority 

 of the Arabian physicians, have believed that they 

 saw in each, great articulation of this taenia, a par- 

 ticular worm. (70) 



§ XV. The head of this taenia has been the 

 subject of many inquiries. 



Welc}iius{7 i) and L{nnaeiis[J'2)ha.\& regarded 

 this worm as being acephalous, 



MJwdius[7S) and Forestii;s{74!) are the first wha 

 mentioned, described and figured the head of this 

 worm as altogether monstrous antl remote from 

 truth. Jllalpighi afterward presented it to us as 

 having eyes, nostrils, a mouth, and teeth, as may 

 be seen in a truly grotesque figure, cited by Le^ 

 clerc.{'7§) We are indebted to Andry^ Tyson, Bon- 

 net, and to Jloederer,[7^) for a more careful and- 

 elaborate description of tlie head of this worm, still 

 further improved by Leske, Pallas, Midler, Block, 

 Goeze and Werner, With the naked eye, we sot^ 

 tliis head armed with two pointed and protuberant 

 appendages, which, by analogy, arc called crotch^ 



