THE CAECUM WORM. 

 Trichocepiialus affinis, Rud. 



Plato XXVIII. 



Description. — Male and female about equal, 40 to 70™'" long. Body whip-like, pos- 

 sessing a short, stout caudal end, 12 to 18'"'" loug, and a very thin hair-like cephalic 

 end of twice this leugth. Tiio latter contains the oesophagus and intestine; the 

 former the reproductive organs and intestine. 



The head is very small and thin, without noticeable papilla? or chitinous arinature. 

 It is said to sometimes have two vesicular, transparent, wing-like inflations. Skin 

 of the neck transversely striate, and when highly magnified shows a serration of the 

 sides indicating cuticular layers which overlap each other like shingles on a roof. 

 (Esophagus and cephalic portion of intestine very minute; its posterior end is large 

 and dark, and empties at the caudal end of the body. On one side of the head there 

 appears to be a canal filled with granules. 



The male is to be distinguished by its tightly-curled caudal end. The testicle, 

 beginning near the caudal end, continues anteriorly as a sinuous tube for about two- 

 thirds the length of the thick portion of the worm ; it then becomes plaited to the 

 end of the thick part, where it turns and continues posteriorly as an enlarged seminal 

 duct for about half the length of the thickened body, where it is constricted ; the 

 remainder continues to the cloaca as a slightly enlarged tube. The intromittent 

 apparatus consists of two parts, an external membranous tube bristling with spiues 

 and an internal long, slim spiculum. It is always found exserted, and usually has 

 one coil in it. The tube shows at its end that the external covering continues 

 around the end into the tube to form a lining membrane, which may be retracted or 

 protruded. There is considerable space between these membranes at the tip, and it 

 assumes various forms, varying between a largo sphere, as shown in the figures, and 

 an elongate cylindrical body. The chitinous spiculum is terminated by an acute 

 poiut. It is from 5 to 6'"'" long, with a width of 0.025'"'". The tube is about three 

 or four times as wide. The spiny points are turned away from tho end. 



The female has a thick body, only slightly curved. Tail, obtuse ; ovary begins at 

 the caudal end, continnes as a plaited canal to the cephalic end of the thick part of 

 body, then contracting returns to tho caudal end where it enlarges, forms a fold, and 

 becomes the uterus, which empties through the sinuous vagina and the vulva at the 

 cephalic end, where the body begins to enlarge. Eggs characterized by having re- 

 frangcnt polar bodies at each end. They measure 0.077'""' in length, including these 

 bodi-es, or 0.0r>6'i>"i excluding them (Raillet). They are elliptical and dark brown. 



Occurrence. — This species is foiiiul in the c?ecnm of sheep, goats, and 



cattle. When the fresh intestine is examined tlie worm may be found 



with its slim, hair-like head firmly sewed into the mucous membranes. 



The serrated structure of the skin not only facilitates the progress of the 



head through the mucosa, but prevents its being pulled backward. The 



thick large end, which is what one really sees at first, appears to float 



free in the intestinal contents. 



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