36 BRISTOL. [Vol. XV. 



which, after giving off several motor nerves, runs to the labial 

 sense organs of three rings (6-8) and to the outer lateral organ 

 of ring 8 in its own segment. This nerve corresponds in the 

 main to a ' middle ' nerve. The sensory ' dorsal branch ' of the 

 ' posterior ' nerve of this segment, as we have seen, is united 

 with the corresponding nerve of segment V. 



" In segment III we find only two nerves, corresponding with 

 the two seen in segment IV. Where is the sensory 'dorsal 

 branch'.? On examining nerve II, we find it contains the 

 missing nerve united with the corresponding nerve of segment 

 II. Nerve II supplies not only the rudimentary eyes (median 

 sense organs) of its own segment, but also the pair of large 

 eyes and the inner lateral organ of segment III. One of its 

 two main branches supplies the outer lateral organ and the 

 labial organs of segment II. 



" Nerve I innervates the median, the inner lateral, and labial 

 sense organs of the most anterior division of the head." 



This species shows also very plainly that some of the meta- 

 meric sense organs acquire eye-like properties in the head 

 region which gradually increase towards the anterior somites. 

 " In no other species hitherto described do we find the sensillae 

 passing by such gradations into the eyes. The sei-ial hoynology 

 of these organs zvitli the eyes is then a fact detnonstrated not only 

 by the ctnbryonic developtnent, but also by the structiiral grada- 

 tions in the adult animal ^ 



In the concluding portion Professor Whitman reviews the 

 evidence derived from the innervation of the head region and 

 says : " The morphological equivalence of segment I with the 

 following segments is evident to a degree that is really aston- 

 ishing. It makes no departure from the typical trunk segment 

 which is not led up to through gradations represented in the 

 segments immediately following it." 



The Nervous System of Nephelis. 



The nervous system of Nephelis may for convenience be 

 divided into two parts : that portion which responds to external 

 stimuli and coordinates the muscles of locomotion, the central 



