NERVUS TERMINALIS: TURTLE 425 



Numerous dissections of embryos and of newly hatched turtles 

 were made with the aid of the binocular microscope. The head 

 was split slightly to one side of the midsagittal plane, and the soft 

 parts were then sufficiently removed to expose the nerve and 

 its adjacent structures. 



The embryos sectioned were cut in the sagittal plane or trans- 

 versely, and were stained by various methods. The most 

 generally satisfactory stain for older stages was found to be 

 iron-hematoxyUn, but some of the most instructive series were ob- 

 tained by overstaining with Delafield 's hematoxylin, followed by 

 a counterstain of saturated aqueous orange G to which two drops 

 of glacial acetic acid were added for each 50 cc. of stain. 



The serial sections studied were -as follows: 



1 series 6-mm. embryo, sagittal, stained with iron-hematoxylin. 



2 series 6.3-mm. embryo, transverse, stained with hematoxylin and Congo red. 



3 series 7.5-mm. embryo, transverse, stained with hematoxylin and Congo red. 

 1 series 8-mm. embryo treated by the Cajal method, cut sagittally. 



1 series 9-mm. embryo, sagittal, stained with hematoxylin and Congo red. 

 1 series 9-mm. embryo, sagittal, treated by Vom Rath method. 



1 series 9.o-mm. -carapace-length embryo, stained with hematoxylin and Congo 



red, sagittal plane. 



2 series 10-mm. -carapace-length embryos, sagittal, stained with iron-hema- 



toxylin. 

 1 series 10.5-mm. -carapace-length embryo, sagittal, stained with hematoxylin 



and erythrosin. 

 1 series 11-mm. -carapace-length embryo, sagittal, stained with hematoxylin and 



Van Gieson's stain. 

 1 series 11-mm. -carapace embryo, sagittal, stained with hematoxylin and 



orange G. 



DESCRIPTIVE 



The nervus terminalis in the turtle has its origin by several 

 small roots from the ventromesial surface of the forebrain, just 

 caudad to the olfactory bulb. It can be demonstrated by dis- 

 section in suitably prepared material. Figure 1 represents a 

 dissection of an embryo of 11-mm. carapace length, showing the 

 left nervus terminalis and its relation to neighboring structures. 

 In the specimen figured the rootlets were not evident until some 

 of the overlying brain tissue had been removed by brushing. By 

 this process three roots were demonstrated. In other dissections 

 but two roots were brought to light, usually after some brushing. 



