ON THE BRAIN OF THE SNAPPING TURTLE, 

 (CHELYDRA SERPENTINA.) 



O. D. Humphrey. 



( With Plates II, III and IV.) 



With the exception of the numerous papers upon the pari- 

 etal eye, the reptilian brain has not been so thoroughly studied 

 as that of many other vertebrate forms. Why this should be so 

 is not easy to determine, for the reptilian brain presents an at- 

 tractive field for the morphologist. While it lacks the primitive 

 structure of the amphibian brain ; in it are found the first ad- 

 vances from the simplicity of the amphibian type, and the begin 

 ning of almost all of the structures that are found in the complex 

 encephalon of the higher vertebrates. Instead of the simple tu- 

 bular form found in the amphibian brain, with the cinerea lying 

 closely about the central cavity, and nerves springing from 

 poorly differentiated areas ; we have here large groups of gigantic 

 cells, great bundles of fibres that are somewhat susceptible to 

 ordinary stains ; strong commissural systems and well marked 

 cortical areas. 



The first mention of the turtle brain was by Carus in 1814, 

 but the first study of it was made by Bojanus in 18 19. Mau- 

 thus, in 1 86 1, studied the spinal cord of the turtle with the aid 

 of the microscope, and W. Miiller, in 1871, made some obser- 

 vations upon the hypophysis. Stieda (85) was the first to make 

 the turtle brain the subject of a monograph, and his work and 

 figures are quoted and copied in many works of very recent 

 date. Meyer gives a careful account of the forebrain in a recent 

 paper (56). In this country Herrick has made many valuable 

 observations on the turtle, as has Spitzka. Osborn has contrib- 

 uted to the knowledge of the commissural systems. Aside 

 from these authors and short references in works of general 

 comparative anatomy, the brain of the CJielonia has been little 

 studied. 



