508 LOCy. [Vol. XI. 



He describes six in the hind-brain of the lizard (Anolis), giving 

 their anatomical characteristics with great clearness. He 

 observed no neuromeres behind the point of origin of the tenth 

 nerve, nor did he find them in the fore- and mid-brain, but he 

 concluded, hypothetically, that they were present in the ante- 

 rior brain regions. Orr found the fifth, seventh and eighth, 

 ninth, and tenth nerves, respectively, connected with the first, 

 third, fifth, and sixth neuromeres of the hind-brain. 



Hoffmann, in Bronn's " Klassen und Ordnungen des 

 Thierreichs " (1888), records his observations on these segments 

 in Lacerta and Tropidonotus. He found seven in the hind- 

 brain of these forms. In the following year he added further 

 details in the Zoologischer Anzeiger. He differs somewhat 

 from Orr as regards the relationships of the cranial nerves, 

 assigning the fifth nerve to the second neuromere of the hind- 

 brain, the seventh and eighth to the fourth, the ninth nerve 

 to the sixth, and the tenth nerve to the seventh neuromere. 

 From the first segment the fourth nerve arises, and subse- 

 quently shifts its position forwards. 



McClure, following Orr's work, demonstrated the segmenta- 

 tion of the neural tube throughout its whole extent, and pub- 

 lished a preliminary announcement of the same in 1889. He 

 showed the presence in the spinal cord of segments continuous 

 with those in the brain, and histologically similar to them. He 

 examined these structures in the chicken, Amblystoma, and the 

 lizard (Anolis). He fixed upon six in the chicken and lizard, 

 and five in Amblystoma, as the number in the hind-brain of 

 each respectively. He found two in the fore-brain, but left the 

 number in the mid-brain undetermined, expressing the view, 

 however, that there are two neuromeres in that brain region. 

 Thus he identifies ten neuromeres in the entire brain region, 

 and agrees with Orr in the assignment of nerves to the 

 neuromeres of the hind-brain. 



Miss Piatt's work (1889), on "Axial Segmentation of the 

 Chicken," agrees, in so far as neuromeric segmentation is con- 

 cerned, with that of her predecessors, except as regards the 

 relation of the nerve-fibres to their corresponding neuromeres. 

 According to her observations they spring, primarily, from the 



