528 ' p. E. SMITH 



Among the earlier workers who noticed foldings in the hind- 

 brain region and attached segmental significance to them, may be 

 mentioned: von Baer ('28), Remak ('50), Dursey ('69), Dohrn 

 (75), Foster and Balfour ('76), Beraneck ('84),Kupffer ('85), 

 Orr ('87), Hoffman ('88), and Miss Piatt ('89). 



In the fore-brain, McClure ('89) working on the chick, Anolis 

 and Amblystoma first described a segmentation and stated that 

 the neuromeres conformed to those of the hind-brain. Waters 

 ('92) confirmed McClure's observations and tried to explain why 

 the neuromeres appeared at such a late stage. Herrick ('92) 

 believed that the neuromeres described for the fore-brain were only 

 dorsal diverticula and not homologous to the ventral diverticula 

 of the mid- and hind-brain. Johnston ('05, '09) described a seg- 

 mentation of the fore-brain, as did Warren ('11). Most of the 

 above workers have described five to nine segments for the hind- 

 brain, two in the mid-brain, two in the diencephalon, and one in 

 the telencephalon. 



Turning now to the problem of the segmentation of the medullary 

 plate, we find considerable diversity of opinion. Zimmerman ('91) 

 found eight 'primare Abschnitte. ' These divided later and formed 

 thirteen. Kupffer ('85, reprinted in '93) found eight neuromeres. 

 Froriep ('91, '92, '93) found in Triton and Salamandra five and 

 four neuromeres respectively. . In his second paper he was 

 skeptical of the segmental value of the neuromeres. Locy ('94) 

 in a preliminary paper, described in Acanthias and Amblystoma a 

 distinct segmentation and in a fuller account ('95) he adds to the 

 number of forms described. Eycleshymer ('95) working on 

 Amblystoma found certain irregularities on the medullary plate 

 and folds but believed that they were artifacts. Neal ('96, '98) 

 was a severe critic of Locy's work. Hill ('00) worked on the chick 

 and teleosts and traced the neuromeres from the medullary plate 

 into the neural tube. Kupffer ('03) was skeptical of Hill's work. 

 Griggs ('10) described for Amblystoma a segmentation of the neu- 

 ral plate but not of the folds. Locy stated that in this form the 

 neural plate was smooth but that the folds were segmented. 

 Smith ('12) found in Cryptobranchus that three transverse 

 grooves appeared in order on the medullary plate and could be 



