6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 70 



of the dorsum. In the adult female it reaches a height of about 23 

 mm., and 19 mm. in the immatures; but this measurement is impos- 

 sible to take with precision. It then disappears as a true ridge at a 

 point from two-fifths to one-half the distance from the anus to the 

 flukes. In the Wulsin juvenile there is only a slight middorsal pro- 

 jection, the lateral boundaries of the future ridge being indicated by 

 a clearly defined groove upon either side, these being 18 mm. apart 

 at greatest divergence and meeting craniad and caudad. 



The middorsal line of all save the adult and the juvenal female 

 is appreciably lighter directly dorsad of the axillary region. This 

 lighter line then increases in width and distinctness until, within a 

 distance of less than 100 mm., it is seen to be compounded of three 

 lines of dots, each line staggered in relation to the one next adjoin- 

 ing. The dots are of a much paler shade than the surrounding 

 integument and they have a composite width of as much as 4 mm. 

 At a point about 400 mm. craniad of the fluke notch (in the imma- 

 tures) they project from the ridge barely sufficiently to be seen and 

 felt as a roughness, but all external evidence, both ocular and tactile, 

 of these disappears at about 250 mm. from the fluke notch. In the 

 adult female and the Wulsin juvenile, however, the dots are appar- 

 ently absent, while in the Hoy juvenile they are more in evidence 

 than in the older females. 



Microscopical examination of a section of the integument cut from 

 the dorsal ridge of the last-mentioned specimen shows that these dots 

 are purely superficial. Klikenthal (1889-1893, 1891) advances the 

 hypothesis that they constitute a vestige of dermal armature. This 

 can not be flatly denied, but there is no reason why these structures 

 should be so considered. Additional microscopical examination of 

 sections of the dorsal ridge prepared at the Johns Hopkins Medical 

 School through the kindness of Dr. Lewis H. Weed and stained with 

 haematoxylene and eosin seems to be conclusive. In these (Plate 1) 

 it is seen that the dots are but a local thickening of the epidermis, 

 evidently colorless in contrast to the surrounding surface. It will be 

 noted that the epidermis of the latter is very thin, the dermal 

 papillae greatly lengthened, and that the latter become coarser and 

 larger beneath the epidermal dots. There is most certainly no sign 

 of cartilage present, much less a center of ossification, and it is hardly 

 possible that they could represent a decadent development from such 

 a condition. 



Flukes. — In one of the females dissected the peduncle was 24 mm. 

 wide at the narrowest point and 57 mm. in height. The dorsal bor- 

 der of the peduncle is sharper or more acute than is the ventral 

 border. The flukes are symmetrically placed and their width varies 

 from 27 and 28.6 per cent of the total length of the immatures to 29 



