SCLEEOSTOMA DUODBNALE. 361 



nematodes, I have frequently noticed the variable character of 

 this colouring, and I have, therefore, ceased to lay much stress 

 upon its presence in the matter of specific identification. 



28. SCLBROSTOMA DUODBNALE. 



8. duodenale, Cobbold. 



Strongylus quadridentatus, Siebold. 



Anehylostoma duodenale, Dubini ; Siebold ; Pruner. 



Ancylostomum duodenale, Diesing ; Leidy ; Kiichenmeister ; etc. 



General and Specific Characters. — ^A small nematode helmintli, measuring usually 

 about -J of an inch in length, the females being sometimes considerably in excess of this, 

 but always less than J" ; characterized especially by an asymmetrical disposition of four 

 unequally-sized, homy, conical, converging, oral papillaB, forming the so-called teeth ; 

 head sUghtly pointed and tapering, contiuuous with a tolerably uniform cylindrical body, 

 ^'' in thickness, and terminating in a straight, cone-shaped, or rather sharply-pointed tail 

 in the female ; the caudal extremity of the male ends in a partially inflexed, blunt point, 

 furnished with a cup-shaped, bilobed bursa, the membranes of which are supported by 

 eleTen chitinous rays, ten being simple, whilst the median, or odd one, is bifurcated at the 

 summit ; m.ode of reproduction viviparous. 



This interesting worm, females and males of which exist in the 

 proportion of three of the former to one of the latter, was first 

 discovered by Dubini at Milan, and though at first thought rare, is 

 now known to be tolerably common throughout Northern Italy. 

 According to Pruner, Bilharz, and Griesinger, it is remarkably 

 abundant in Egypt, the latter authority supposing that about one- 

 fourth of the people are constantly suffering from a severe angemic 

 chlorosis, occasioned solely by its presence in the small intestines. 



From the accurate descriptions of Siebold, it become^ quite 

 evident that this worm is closely allied to his genus Syngamus ; and, 

 as he has himself remarked, it might have been placed in the genus 

 Sclerostoma. In this genus I have arranged it, because the asymme- 

 trical disposition of the so-called dental organs is not, of itself, suffi- 

 cient for the estabhshment or retention of Dabini's genus Anehy- 

 lostoma ; otherwise, out of respect for the discoverer, I would 'have 

 preferred his nomenclature. Sclerostoma diiodenale- closely resem- 



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