438 Leland Griggs. 



divided into metencephalic plate and spinal cord plate, although 

 in Amblystoma there seems to be no trace of a dividing groove. 



Connected with the neural plate are some less important 

 structures which should be defined. The narrow groove bound- 

 ing the neural plate will be called the peripheral groove. The 

 low ridge running around the neural plate just outside the peri- 

 pheral groove will be called by its usual name of neural crest. 



In Amblystoma the neural plate undergoes at an early period 

 a sharp downfolding. This will be called the infundibular de- 

 pression. 



The term neuromere is one that needs careful definition. In 

 this paper it will be applied to the early divisions of the neural 

 plate which have been called primary neuromeres. These divi- 

 sions are considered as having true metameric value. The 

 later divisions of the neural tube will be called neuromeres in 

 so far as they can be shown to be identical with the divisions 

 of the open neural plate. The use of such terms as primary 

 and secondary neuromeres will be avoided because they are 

 contradictions of the idea that a neuromere is a genuinely seg- 

 mental structure. 



To sum up, the old terms neural plate, neural crest and neuro- 

 mere will be used substantially as they have been used before, 

 while the term neural groove will be used in a new and restricted 

 sense. The new terms, blastogroove, anterior germinal depres- 

 sion, posterior germinal depression, peripheral groove, trans- 

 verse cephalic groove, procephalic lobes, infundibular depression 

 are new terms applied to newly discovered structures or to 

 newly discovered divisions in old structures. 



Material and Methods 



Amblystoma punctatum was the animal chosen for study, 

 mainly on account of the large egg which when first laid is about 

 two mm. in diameter. This is larger than any frog's egg and 

 much larger than the egg of Amblystoma tigrinum but con- 

 siderably smaller than the egg of Necturus. The anlage of 

 the nervous system of Amblystoma punctatum, however, is 



