HARRIMANIA MACULOSA II7 



ing to the protochordata are deserving of high regard, has ex- 

 pressed the view that "What has been called the notochord in 

 the Enteropneusta does not correspond with this definition [of 

 it as used in the Chordata] except in its capacity of skeletal 

 product of the gut wall." And he proposes for it the term 

 ' stomochord,' though declaring at the same time that " this term 

 involves no sacrifice of conviction whatever, since it leaves the 

 question of the morphological relationships of the structure to 

 which it refers quite open." From the evidence now at hand it 

 appears to me there can be no serious doubt that we have in this 

 organ the immediate genetic forerunner of the vertebrate noto- 

 chord, and that it does not differ sufficiently cither in structure 

 or relations from the essential nature of the vertebrate organ 

 to zvarrant giving to it as a whole a different designation, 

 I shall, consequently, follow Bateson and call it the notochord. 

 The anterior pouch-like portion of the organ, the part corre- 

 sponding to the entire organ as it exists in the adults of other 

 species, I shall speak of as the nuchal notochord ; and the 

 trough-like, posterior portion as the esophageal notochord. 

 These terms I adopt as having reference not merely to the mor- 

 phological relations of the respective parts — the nuchal noto- 

 chord being situated chiefly within the neck or peduncle, while 

 the esophageal notochord is in the esophagus — but also from the 

 functional relations which I conceive to have been the prime 

 factor in differentiating the organ into these two distinct parts. 

 The nuchal notochord^ has in all probability been produced sec- 

 ondarily from the original simple structure in coordination with 

 the development of the proboscis and neck. This view has 

 been held as a theory by various authors, but hitherto the only 

 direct evidence in support of it has been the longitudinal con- 

 striction on each side of the esophagus behind the notochordal 

 evagination in the embryo, observed by Bateson (1884) and 

 Morgan (1891). But the imperfect knowledge of the histor3'of 

 these constructions has left their significance in doubt until now. 

 Concerning the structure of the nuchal notochord, little need 



' Willey 's term ' stomochord ' might well be retained for this part, but for the 

 fact that a separate substantive applied to it in this way would imply that it is 

 an independent organ, and this the facts do not warrant. 



