332 HORACE W. STUNKARD 



importance. Von Kupffer ('85) observed a 'primary metamerism' 

 in the neural tube of Salamandra atra embryos which appeared 

 before the segmentation of the mesoderm, and Orr ('87), studying 

 the embryology of the lizard Anolis, noticed a number of symmet- 

 rical constrictions in the lateral walls of the hindbrain, '' giving 

 the walls in horizontal section an undulated appearance." 

 Kupffer called these 'medularfalten' and Orr adopted for them 

 the name neuromeres. This author formulated the first criteria 

 for determining the identity of the neuromeres. He described 

 two in the primitive forebrain, one in the midbrain, and six in 

 the hindbrain. McClure ('90), working on embryos of Amblys- 

 toma punctatum, Anolis sagroei, and the chick, found "a con- 

 tinuous and symmetrical series of neuromeres increasing in 

 size anteriorly, which extend from the lateral walls of the em- 

 bryonic brain, throughout the entire length of the neuron." He 

 believed that the primary forebrain contained two neuromeres, 

 that the midbrain consisted of two neuromeres, and that the 

 third and fourth nerves were the nerves of these somites. Froriep 

 ('91) found neuromeres prior to the segmentation of the meso- 

 derm, but did not attach any segmental importance to them, and 

 later ('92) decided they were the results of underlying meso- 

 blastic somites. He found the constrictions in the median 

 part of the cephalic plate, while the neural tube is still open, 

 four in Salamandra maculosa and five in Triton cristatus. 

 Waters ('92) confirmed the observations of McClure, and found 

 three segments in the forebrain. Eycleshymer ('95) observed 

 certain markings in the neural folds which might be interpreted 

 as neuromeres, yet he noted that their arrangement was decidedly 

 irregular and the structures were probably due to the action of 

 killing reagents. The transverse markings in the neural plate 

 he regarded as due to the formation of the myomeres. 



The tendency to regard the neuromeres as segmental struc- 

 tures reached a definitive stage with the work of Locy ('95). 

 This author reviewed the w^ork on neuromeres exhaustively. 

 He made observations on Squalus acanthias, Amblystoma, 

 Diemyctylus, Rana palustris, Torpedo ocellata, and the chick. 

 In all these forms he described neuromeres in very early stages, 



