436 Leland Griggs. 



creased in bulk by appropriating other tissues. To prove the 

 correctness of this view it would be necessary to show that the 

 anlage of the eyes does not lie on the neural plate. If we turn 

 to work outside the field of amphibian embryology for evidence 

 we find that the neural plate is not very sharply marked off 

 from the neural crests in those animals which have been studied 

 most. Fororiep ('05) locates the '^Sehgrube" of Torpedo on 

 the edge of the neural plate in the area called by His ''Flugel- 

 platte," and Locy ('95, '97) locates the optic groove of Acan- 

 thias and the chick on the sides of the neural furrow as the walls 

 begin to rise to form the canal. None of these forms, however, 

 has a clearly marked groove between the neural plate and the 

 neural crest and therefore, although these authors seem to 

 believe that the eye spot is located on the anlage of the brain, 

 it is clear that this interesting point still remains unproved. 



Locy's work on Acanthias is especially interesting inasmuch 

 as he was the first to find '^accessory optic vesicles." He ob- 

 served that the first, or true optic groove, covered the space 

 of three neuromeres and following this was a series of five or six 

 accessory vesicles occupying the space of one neuromere each, 

 although this relation to neuromeres was not always strictly 

 observed. Locy has compared this arrangement with that of 

 the same organs of the leech embryo described by Whitman 

 ('89). In the process of development the accessory vesicles 

 degenerate except the first pair which according to Locy form 

 the pineal eye. A study of the chick confirmed the work on 

 Acanthias. 



This review of the literature dealing with the problem of the 

 development of the nervous system of the Amphibia has revealed 

 the need of further research along several lines. First, the series 

 of early grooves which appear at about the same time as the 

 neural plate should be carefully investigated and their relation 

 to the nervous system determined. Then attempts should be 

 made to trace Kupffer's primary neuromeres into the later divi- 

 sions of the brain, and the exact position of the anlage of the eye 

 should be determined and also its relation to numbered neuro- 

 meres. 



