54 



McCLURE. [Vol. IV. 



EXPLANATION OF PLATES. 



Index Letters. 



/«, Iln, Illn, IVti. First, second, third, fourth, etc., cranial nerves. 

 Ant. Anterior. 



Ap. Apex of internal ridge of neuromere. 

 Aud. Ves. Auditory vesicle. 

 Ep. Epiblast. 



Ex. Pit of external depression of neuromere. 

 FB. Rudiment of secondary fore-brain. 

 HB. Hind-brain. 

 itt. Inner surface of neuromere, or that surface of the neuromere which 

 lines the neural canal. 

 MB. Mid-brain. 

 Mes. Som. Mesoblastic somite. 

 Myl. Myelomere. 

 Na. Nasal thickening of epiblast. 

 A^m I. Olfactory neuromere. First neuromere of the primitive fore-brain. 

 Nm II. Optic neuromere. Second neuromere of the primitive fore-brain. 

 Nm II J Possibly a portion of a third neuromere of the primitive fore-brain. 

 Nm V. Trigeminal neuromere. First and most anterior neuromere of the hind- 

 brain. 

 Nm VI. Abducens neuromere. Second neuromere of the hind-brain. 

 Nm VII. Facial neuromere. The third neuromere of the hind-brain. 

 Nm VIII. Auditory neuromere. Fourth neuromere of the hind-brain. 

 Nm IX. Glossopharyngeal neuromere. Fifth neuromere of the hind-brain. 

 Nm X. Vagus neuromere. Sixth neuromere of the hind-brain. 

 Nu. Nuclei. 



Out. Outer surface of neuromere. 

 Op. Ves. Optic vesicles. 

 Spn. Spinal nerve. 

 Spt. Neural septa. 

 Thai. Thalamencephalon. 



All figures of sections have been drawn with the Abbey camera lucida and a Zeiss 

 microscope. Z. 2 A means Zeiss ocular 2, and objective A, etc. 



