the Origin of Intestinal Worms. 349 



Bots or horse-flies too {CEstrua equi), always appearing first 

 in the dung of this quadruped, who could have anticipated the 

 real source whence it sprung ! It is now known, beyond dis- 

 pute, that the parent fly deposits its ova upon the coat of a 

 horse, within reach of the animal's tongue ; that these are in- 

 troduced into the animars stomach without being injured ; that 

 tliere the larvae are disclosed, and immediately attach themselves 

 to the mucous surface of the stomach, and at last pass through 

 the whole length of the intestinal tube, and are discharged. 

 And^ moreover, the newly-discovered metamorphoses of the 

 Cirriped animals and the Lernce, described in the magnifi- 

 cent memoirs of Nordmann (Mikrographische Beitrage), m 

 the researches of John V. Thompson of Cork and of others, 

 do they not all tend to demonstrate that a variety exists in 

 the development of the lower animals, which surpasses the 

 imagination of man ? Such facts having been revealed to 

 the naturalists of our day, surely many others equally mar- 

 vellous are reserved for naturalists of future times. As for 

 the intestinal worms, all things tend to prove, that the greater 

 the difficulties which these animals experience in conveying 

 their young to the appointed places of safety, the more strange 

 and peculiar are the means employed by them for that pur- 

 pose, under the provident bounty of nature. Respecting these 

 means, abundant hypotheses may be proposed. The fact, for 

 example, that the flesh of fishes in summer is often bestudded 

 with small worms (which, in one instance, I ascertained to be 

 Echinorhynchi), might lead to the supposition that it is the 

 breeding-place of some species ; the same suggestion might be 

 offered with regard to the small twisted worms often found in 

 the flesh and cellular tissue, and commonly called Filariae ; 

 the Trichina spiralis, discovered by Owen, may perhaps be- 

 long to the same category ; and all vesicular worms may be 

 regarded as the earlier states of other species, an hypothesis 

 which is strengthened by the fact, that no reproductive or- 

 gans have been found in them, an occurrence always marking 

 an early stage of development in intestinal worms. The 

 monthly exacerbation of symptoms observed in helminthiasis, 

 the itching of the nose in children suffering from worms, may, 

 somehow or other, be connected with the history of these 



VOL. XXXI, NO. LXII. — OCTOBER 1841. S 



