84 Journal of Comparative Neurology. 



The greater part of tlie paper deals with the brain of the 

 adder, Callopcltis ivscjilapii. 



The histolog-ical elements are so grouped that a number of 

 fields are rather sharply distinguishable. The cells may be dis- 

 tinguished by their position as well as their form in several 

 classes which are mentioned rather for convenience than as his- 

 tologically distinct types. (i) Cells with multiangular, often 

 pyramidal nuclei surrounded by a relatively small protoplasmic 

 body, more or less parallel to the nucleus. These form the 

 mantle layers. (Figured by Edinger, Plate IV, Fig. 36.) (2) 

 Cells with round nuclei situated either centrally or near the wall 

 in a clear space. These may be isolated or grouped in nests of 

 from two to six cells somewhat resembling cartilage cells. 



The present writer has already discussed these differences 

 at length in several papers and has laid off the cortex into areas 

 or "lobes" with their respective niduli each distinguished by 

 the form of the cells. If any thing is needed to complete the 

 evidence that these distinctions have physiological significance, 

 it is found in the fact that the pyramidal cells lie in areas which 

 are tributary to the ventral peduncles. The suggestion of Brill 

 that the greater part of corte.K is homologous with the subicu- 

 lum cornu ammonis may be regarded as gratuitous assumption. 

 The " fronto-median lobe" seems to be homologous with the 

 limbic region of higher vertebrates and is of the flask-shaped 

 type (sensory). As in mammals, the motor areas are mingled 

 with sensory cells, so there is no exclusive seggregation in rep- 

 tilia. The statement of Meyer that the processes of these cells 

 can only be detected by Golgi impregnation requires modifica- 

 tion. 



The cell-nests of the axial lobe which Meyer compares to 

 cartilage cells, have been described by the writer in the alligator, 

 lizards, serpents and fishes, and by C. H. Turner in birds, and 

 constitute a remarkable structural modification, for which the 

 theory of proliferation has been proposed — a theory which adds 

 probability to the view of Edinger and the writer that the 

 hippocampus and other parts of the cortex are progressively 

 thrust out from the axial lobe. Meyer follows Edinger in call- 



