HARRIMANIA INIACULOSA 121 



as more primitive, and I should certainly agree with him in this 

 view. The epibranchial ridge of Harrimania is of the same 

 type as that of the species of Balanoglossiis above mentioned, 

 and it is here, as I have already pointed out, that its histolog- 

 ical structure is notochordal in character. Unfortunately Spen- 

 gel was unable from scarcity of material to study exhaustively 

 B. canadensis^ and he gives us no information about this struc- 

 ture beyond the fact of its great breadth. Fig. 8 represents 

 a section of the epibranchial band and the adjacent dorsal 

 ends of a pair of septal bars between which it is included. The 

 thickness of the epithelium, the complete absence of nuclei and 

 of staining in the outer half of it, and the large, crowded, 

 irregular, deeply-stained bodies among the nuclei in the inner 

 half, make the band a striking object in a general view of the 

 section of the animal as a whole. The wall of the gut ventral 

 to the pharynx, not shown in the figure, is entirely different. 

 In the first place it is scarcely more than half as thick. Struc- 

 turally the nuclei are abundant to its very outermost stratum, 

 and the long, narrow cell-bodies belonging to them can be seen 

 stained, to some extent, through the entire thickness of the wall. 

 Careful examination of sections of the band with higher mag- 

 nification, and a comparison of these with sections of the nuchal 

 notochord in the same individuals, convinces one of the close 

 similarity of the two. What appear to be sharply defined fibers 

 anastomosing with one another in a complicated way, with' a 

 few small nuclei scattered here and there at the points of anas- 

 tomosis, and with large vacant spaces among the fibers, are the 

 characteristics which distinguish both tissues alike. The abrupt- 

 ness with which the epithelium of the band passes over into the 

 much thinner, fully nucleated, and non-vacuolar epithelium, lin- 

 ing the inner surface of the branchial bar, will also be noted 

 {e^, b. and br. e^.^ fig. 8). 



Having now presented in outline the facts relative to the pres- 

 ence of an esophageal notochord in Harrimania maculosa, and 

 also those which suggest that the epibranchial band in this 

 species is to be interpreted as a continuation of the notochord 

 into the pharynx, we may inquire whether there is any evidence 

 afforded by other species of Enteropneusta of the presence, 



