198 TAPEWORMS OF HARES AND RABBITS STILES. VOL.XIX. 



DAVAINEA SALMONI, Stiles, 1895. 



(Plate XXII, figs. 3-4; Plate XXIII, figs. 1-9; Plate XXIV, figs. 1-2 ; Plate XXV, 



figs. 1-11.) 



1887, " Tcenia pectinata," GOEZE, 1782, of CURTICE exparte, Science [N. Y.], March 23. 

 1895, Davainea salmoni, STILES, Veterinary Magazine, II, June, p. 343. Aug. 28, 1895. 



The length of type specimen, mounted (Bureau of Animal Industry 

 Cestode series No. 1196), is 86 mm.; the broadest segments attain 3 mm. 

 in width. Total number of segments about 450 (the exact number could 

 not be ascertained because of contraction at certain points), of which 

 about 230 belong to the first third of the worm. Head 0.736 mm. broad 

 by 0.496 long. Retracted rostellum 0.144 mm. in diameter, provided 

 with a double crown of minute hooks, of characteristic Davainea form, 

 20 j.i long, about 60 hooks in each row. The suckers are large and 

 prominent and armed with rows of closely set hooks, the number of 

 which it is utterly impossible to count; they may be estimated at about 

 750; the size of these hooks varies, the prong of the longest reaching 

 10 jj. The neck is thin (0.480 mm. broad) and short, segmentation 

 beginning about 0.8 mm. back of the head. The segments vary extremely 

 according to contraction, most of them being broad and short, but 

 others being infundibuliform and nearly as long as broad. Within the 

 proximal third of the strobila variations may be found between seg- 

 ments 0.512 mm. broad by 32 fj. long and 0.7 mm. broad by 0.528 mm. 

 long. 



.The anlage of the genital organs first appears in about the one 

 hundred and seventieth segment, as a darkly staining body, one end 

 of which is in the median line, the other pointed toward the pore side 

 of the segment. As the segments are followed distally this body 

 assumes the characteristic pistol shape found in the genital anlagen of 

 so many tapeworms (Moniezia, etc.); the muzzle of the barrel rapidly 

 reaching the lateral margin at the genital pore; the barrel divides into 

 two parallel canals, the vas deferens proximally, the vagina distally, 

 while the handle of the pistol grows distally in the median line to form 

 the female glands in approximately the middle of the segment. The 

 genital pores are irregularly alternate, and vary in position from the 

 middle to near the anterior edge of the margin. The testicles appear 

 at about the two hundred and thirtieth segment, and occupy almost 

 the entire median field. The condition of the material does not warrant 

 a description of the changes the female anlage undergoes, further than 

 to state that the glandular portion divides into two (or probably three) 

 bodies. The anterior body will by analogy represent the ovary, the 

 distal body the vitellogene gland; the third (very indistinct) body 

 would probably represent the shell gland. Canals could be seen 

 between these glands, but could not be analyzed. The development 

 of the uterus could not be followed, but after about the three hundred 

 and fortieth segment groups of eggs gradually appear, suppressing 



