5IO LOCV. [Vol. XL 



Froriep gave a noteworthy contribution to the subject of 

 neuromeric segmentation in very early stages, before the Ana- 

 tomische Gesellschaft of Germany, at the June meeting in 1892. 

 He described anew the so-called neuromeres that he had previ- 

 ously observed in mole embryos, but concluded that they are 

 not of true morphogenetic significance. He further described 

 the conditions in Triton embryos, and concluded that the 

 so-called primary neuromeres detected by Kupffer in those 

 animals are simply the result of underlying mesoblastic somites. 



Froriep agrees with Kupffer in finding segmental folds 

 while the neural groove is widely open, and in locating them 

 in the median part of the cephalic plate. But, whereas Kupffer 

 finds eight in the brain region of Salamandra atra, he finds 

 only four in the corresponding region of Salamandra maculosa, 

 and five in Triton cristatus. (Compare with my observations, 

 p. 529.) His general conclusion is that "the jointing of the 

 vertebrate body is originally determined by the middle germ- 

 layer; when ectodermal structures exhibit segmental arrange- 

 ment, it is the result of secondary, adaptation." 



Herrick ('92), in a preliminary paper, gives an account of 

 neuromeres in the Ophidian embryo, in stages after the com- 

 plete closure of the neural groove, and after the formation 

 of the ear vesicle. His figures show six neuromeres in the 

 medulla. He states a proposition that will be of use later, in 

 helping to distinguish between primary metamerism, and meta- 

 meres of secondary origin which show after the closure of the 

 neural tube: "If neuromeres once existed in the fore-brain 

 they would be visible only at an early stage . . . The so-called 

 fore-brain neuromeres differ from those of the medulla and 

 cord in involving only dorsal structures." 



The present writer, in 1894, gave the first account connect- 

 ing the earliest formed neuromeres with those of later stages. 

 He showed that in sharks they arise very early, and may be 

 traced without a break through all the stages of the open 

 neural groove into the structures that have, in later periods, 

 been designated neuromeres. The segmental divisions extend 

 to the anterior tip of the fore-brain, and are distinguishable in 

 that region for a brief time after the closure of the neural groove. 



