155 



DocHMius CERNuus, Oreplin. 



Plate XXII. 



Deseription. — Female, 20 to 26™™ ; male, 13 to 17™™. Body very dark colored wlien 

 fresh; whitened when preserved; atteuuate towards the ends. Head curved, the 

 mouth being directed dorsally. Mouth round, smaller than the oral surface, and 

 opens into an ovoid dark-colored capsule. About the opening stand four teeth, two 

 on each side, their base being sunk into the capsule and their free edges projecting 

 into the cavity. The ventral are the larger, thicker, and more opaque ; their edges 

 form an unbroken sinuous line. At the caudal opening of the capsule are one pair of 

 ventral and a single dorsal tooth; the latter is conical, very large, and risos to near 

 the mouth. In the pharyngeal opening are six very small club-shaped, spinous, 

 chitinous appendages of the oesophageal supports or rods ; they seem to be jointed. 

 There are six papillae — dorsal, lateral, and ventral pairs. The lateral may give off 

 a branch on the dorsal side. There are two lateral neck papillss, nearly opposite the 

 middle of the oesophagus; the ventral cleft is situated a little anterior to a line con- 

 necting the latter. Unicellular neck glands quite plain. 



Male: Bursa funnel-shaped ; will not spread without tearing; costse unsymmetrioal 

 as to form ; ventral pair not separated ; lateral, widely separated ; dorsal notched ; 

 dorso-lateral unequal in length and differently attached to the dorsal stem. Spicula 

 0.6™™ long, aculeate, fenestrated, and provided with a narrow membranous margin. 



Female: Vulva about three-fifths of the entire length of the body from the end of 

 the tail. Vagina. opening at right angles to the side of the body. Uteri, lying one 

 anterior, the other posterior; each forms an S-like loop; the anterior ovary is di- 

 rected towards the tail, and, with the posterior, forms an intricate sinuous net-work 

 surrounding the intestine. Eggs elliptical; laid in the morula stage; length, 0.06™™; 

 width, 0.03™™. 



Occurrence. — This species inhabits the small iutestine of sheep, and 

 attaches itself to the intestinal walls by its stout oral armature — the 

 so-called teeth. It lives upon the blood of its victims. 



The life history of this species of Dochmius has not been determined, 

 but there is no reason for supposing it different from that of JD. trigo- 

 nocephalus, the allied species found in dogs. This life history has been 

 determined by Leuckart {Die Menschlichen Parasiten, Baud II, pp. 132- 

 134), and is essentially this: The eggs pass from the dog to the ground, 

 -wliere, in wet places, they uudergo a development of the vegetative 

 organs. If at this stage the young are swallowed by another dog they 

 develop into adults. The development outside the dog may consume 

 from three to six days. The worm may then continue living without 

 further development for an indefinite time, depending on the conditions 

 by which it is surrounded and the favorable opportunities for being 

 eaten by the dog. Its development in the dog occupies about two 

 weeks. The time consumed may be supposed to be that occupied by 

 the development of Dochmius cernuus with approximate certainty. 

 Leuckart states that though he saw some of the embryos enter snails 

 while in their free living state, that this condition was an unnecessary 

 one, and that the worms underwent no development while in the snails. 

 It may be that if these parasites can enter the snails, their opportuni. 



