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Pr, sluiteri) innervated by a subradular system of connectives and 

 ganglia with relations essentially similar to that of the chitons. In 

 addition there is a dorsal and ventral commissure arising in the neigh- 

 borhood of the subradular connectives. These same elements occur 

 also in Rhopalomenia scandens, and to a certain extent in another 

 Neomenian whose anatomy will be described in a forthcoming report. 

 It thus becomes apparent that the well known ganglia, imbedded in 

 the pharynx, are not strictly buccal, but probably correspond to united 

 buccal and labial ganglia, and the connectives arising from the brain 

 are therefore labio-buccal. 



I wish once more to emphasize the fact that the subradular system 

 and the connectives are, except in very carefully preserved material, 

 very difficult to follow, and even then may only be traced with certain- 

 ty by the aid of accurate micrometric measurements and often with 

 the use of an oil immersion lens. There is no doubt that they exist, 

 and the fact is rendered more certain for the reason that I have re- 

 cently found a subradular organ and characteristic nerve supply in 

 several species of the highly modified genus Chaetoderma. 



In two species of Chaetoderma, from Alaska, that I preserved in 

 VOM Rath's fluid, there is a well marked ridge in the pharyngeal epi- 

 thelium in the mid line directly in front of the peg-like radula. In 

 material killed in alcohol the ridge is distinguishable, but it is not 

 sharply differentiated from the neighboring epithelium. In cross sec- 

 tions a ganglionic mass is seen a short distance beneath this organ, 

 and in one species it shows slight signs of being double (as it doubt- 

 less is in early life), but generally it is single and is placed in the 

 mid line (Fig. 1 s). Right and left it developes a nerve which proceeds 

 laterally, imbedded in the pharyngeal musculature, to join the labio- 

 buccal connective. In its course each of these nerves gives rise to a 

 relatively strong branch that passes to the base of the subradular ridge 

 described above; and still more laterally it expands considerably in 

 originating a nerve passing into the pharyngeal musculature where it 

 soon becomes lost. In alcohol killed material the ganglion in some 

 species, for example Ch. nitidulum, superficially resembles one of the 

 groups of salivary gland cells, but the nerves are usually not especially 

 difficult to trace. 



In another genus, Limifossor, belonging to the family Chaeto- 

 dermatidae, I^) have called attention to what appeared to be a sub- 



1) H. Heath, The Morphology of a Solenogastre, in: Zool. Jahrb., 

 Abt. f. Anat., Bd. 21, 1905. 



