270 AMERICAN JOURNAL 



Acmreid^e ; but, after the examination of a large multitude of 

 specimens, I regret that I cannot confirm his observations in 

 these two particulars. 



The nervous system has been examined by Garner, Rhymer 

 Jones and Anderson, and, later and much more thoroughly and 

 correctly, by Brandt (Bull. Acad. Sci. St. Petersburg, Nov. 24, 

 1868). The whole system is naturally arranged in two groups, 

 the cerehro-pharyngeal and the pedo-hraneldal nerves and gang- 

 lia. These two groups are connected on each side by two slender 

 commissures. The principal ganglia of the first group are the 

 cerebral and pharyngeal ; of the second, the ganglia pedalia and 

 visceralia. The whole paper is so concise, and the nervous sys- 

 tem so intricate, that tlie student is referred to the original, 

 should more detailed information be required. Dr. Brandt 

 having set at his work with the preconceived notion of the close 

 affinities of Chiton and Patella, finished without changing his 

 mind on the subject; but the unprejudiced student, on compar- 

 ing the figures of the nervous system of Ohito7i fascieularis mpon 

 the same plate with that of Patella, will hardly be disposed to 

 agree w'ith him. Indeed, the further the embryology and minute 

 anatomy of the two groups are carried, the more evident does 

 their dissimilarity become.* 



It is not a little astonishing that, of all the authors who have 

 commented upon the nervous system of Patella as given by Cu- 

 vier, not one seems to have recognised the fact that it is not 

 that of Patella vulgata at all, but (t robably) that of Patina pel- 

 lucida, an animal belonging to a different genus. Some of the 

 discrepancies may be )'econciled when the latter comes to be dis- 

 sected. Neither of the species dissected by Cuvier can be rec- 

 ognized by anything in his article as published in the " Memoires.'' 

 They are generally supposed, however, to be vulgata and pellu- 

 cida. In noticing the optic nerve Dr. Brandt calls attention to 

 the fact that the eyes are situated upon the superior surface of 

 the base of the tentacle, and not upon a tubercle at the outer 

 base, as usually stated, and, I may add, not upon the prominent 

 tubercle at the inner base, as Cuvier supposed. 



The digestive system has been treated by Cuvier and Lankes- 

 ter. The latter has added little to the labors of his predecessor, 

 and appears not to have read his "Memoire," or at least to have 

 overlooked the descriptions and figures (p. 18, pi. ii, f. 7, 12) of 

 the crop and salivary glands, as he claims them as a discovery of 



* Nevertheless, the typically molluscan nature of the nervous system 

 of Chiton, and the fact that it is somewhat allied to the Patellidae, may 

 be considered as proven by Brandt's investigations. There is room for 

 investigatioB with regard to possible atiinities with Brachiopoda. 



