136 H. V. NEAL 



The main objection to the use of neuromeres as essential cri- 

 teria of metamerism is not so much their variabiUty in different 

 vertebrates or the diversity of opinion among morphologists 

 regarding them, as it is the difficulty of finding criteria by means 

 of which the coenogenetic may be distinguished from the palin- 

 genetic, especially in the regions of the forebrain and hindbrain. 

 In an earlier paper ('98)* the writer protested against the uncriti- 

 cal acceptance of all sorts of foldings of the central nervous 

 system — dorsal, ventral or lateral — as evidence of the primary 

 metamerism of the nervous system. Special protest was raised 

 against the claim of Locy ('95) that he had been able to trace 

 the ^primary' neuromeres of the open neural plate into the neu- 

 romeres of the closed neural tube. Eycleshymer ('95) and Kings- 

 ley ('97) were likev/ise unable to accept Locy's assertions. 



Hill ('00), however, confirmed Locy's results by his observa- 

 tions on teleost and chick embryos and considered Neal's objec- 

 tions as 'negative.' Wilson and Hill ('07, p. 147) on the other 

 hand ''cannot admit that Hill has fully and adequately met 

 Neal's objections to Locy's interpretation of the early crenation 

 of the margin of the cephalic plate, for example, in Squalus. The 

 weightiest part of Neal's contention, as it appears to us, is not 

 merely negative, as C. Hill represents it, but resides in the posi- 

 tive statement that the beaded thickenings found are not only 

 asymmetrical but are quite variable in different specimens." 



Johnston ('05), ignoring Neal's objections, accepts the results 

 of Locy and Hill on the ground that "the work of these last two 

 authors is evidently most painstaking and their results are so 

 complete and so far in agreement that they may be taken to 

 represent the present state of knowledge of the neuromeres." 

 Yet von Kupffer ('06, p. 164), working on chick embryos, finds 

 that Hill's 'astonishing pictures' of the neuromeres of the chick 

 give the impression that "the subjective motive of the investi- 

 gation had influenced too much the completion of the drawings." 

 Kupffer states (p. 248) that in spite of equally extended obser- 

 vations he was not able to confirm Hill's results. Graper ('13) 

 also has been unable to find Hill's neuromeres in the chick. 



