5o6 LOCV. [Vol. XI. 



with the visceral arches, and with the cranial nerves " which 

 grow with them." According to his observations they fade 

 away after the fifteenth day. 



Dursy observed them in 1869, in the embryonic cow, of 

 6.5 mm. in length. He recorded the occurrence of six folds in 

 the region of the fourth ventricle. Foster and Balfour, in 

 1874, noted the same structures in the chick, and suggested 

 that they were of segmental importance. Dohrn, in 1875, 

 called attention to the occurrence of eight or nine neural seg- 

 ments in the fourth ventricle of bony fishes. He contrasted 

 this early segmentation with segmental divisions in insects. 

 Gotte figures such segments in the hind-brain of well-developed 

 embryos of Bominator. In 1877, Mihalkovics was inclined to 

 interpret these segments as due to mechanical pressure of the 

 mesoblast, and, therefore, not a fundamental feature of the 

 medullary tube. 



Beraneck showed, in 1884, that there is a definite connection 

 between certain of these segments and cranial nerves, thus 

 giving the first real foundation for establishing their segmental 

 relations. In his earlier paper, he describes five pairs of trans- 

 verse folds in the hind-brain of embryos of Lacerta agilis from 

 3 to 4 mm. in length. He noticed that they rapidly fade away 

 and disappear in embryos 5 or 6 mm. in length. In 1887, he 

 studied the relations of these "replis medullaires " in the chick, 

 and, as regards their connection with cranial nerves, reached 

 similar conclusions. 



Kupffer maintained in 1885 that these segments indicate a 

 primary metamerism of the medullary tube. He has published 

 several brief notices on these structures. In 1884, he gave a 

 record of studies on the brain of the trout, in which he found 

 five pairs of neural segments in the hind-brain. In sagittal 

 sections he noted, in addition to these, three pairs in the mid- 

 brain. He found no segments further forwards, and concluded 

 that the fore-brain is not to be included in the segmented 

 region. 



In the following year ('85) he gave the results of his 

 studies on embryos of Salamandra atra. In embryos of that 

 form, showing as yet no traces of protovertebrae, he found 



