561 



of this point. The successive sections bring into view the delicate 

 rootlets which arise from both rhombomeres. 



The auditory vesicle is situated opposite rhombomeres 5 and 6, 

 as is apparent from a comparison of Figs. 3 and 4 which were photo- 

 graphed under the same powers. 



Behind the 6th rhombomere the hind brain is practically in- 

 distinguishable from the spinal cord, and in this latter portion of the 

 brain as in the spinal cord the neuromeres are very slightly marked. 

 Even the 7th and 8th rhombomeres, so plainly marked in the gull, 



Fig. 1. Rabbit. Sagittal section through rhombomeres 2 — 6. The abducent is 

 marked 'VF. 



are no better developed than those which follow them. Both, however, 

 can be traced through a number of sections; it is to these segments 

 that the IXth and Xth nerves are connected. Three somites are re- 

 presented in the hypoglossal region of the embryos which have been 

 especially examined, and these are accompanied by their respective 

 ventral roots. 



The brain of one of the embryos has been reconstructed, and the 

 diagram, Fig. 2, serves to show more plainly the encephalomeres and 

 the relationship of the cranial nerves to them. There is no need to 

 explain the results at length for they are in entire agreement with 

 those obtained with reference to the species described in former papers. 

 It will be seen from the diagram and still more forcibly from Figs. 3 



Anat. Anz. XXXVI. Aufsätze. 



36 



