351 



brain along with the sensory nerves, that is to say, these nerves are 

 nerves of the lateral cornu (Seitenhornnerven). The muscles therefore 

 are not metameric body muscles. 



The sensory nerve to the third tentacle is a branch of the Ramus 

 maxillaris Trigemini (= Ramus coronoideus, mihi). This large branch 

 divides into two branches by the side of the rootpiece and these into 

 smaller twigs which ensheath the cirrus. 



The parts of the whole structure are therefore. 



1) Free portion or cirrus. 



2) Rootpiece. 



3) Intertentacular muscles. 



4) Motor nerves (not ventral spinal nerves). 



5) Sensory nerves. 



Turning now to Amphioxus we find that every one of these 

 characteristics is presented by the oral cirri. The free portions of 

 the cirri correspond to the free portions of the tentacles in Myxine, 

 rootpiece corresponds to rootpiece, the muscles of Myxine are repre- 

 sented by the ejaculatory muscles of Amphioxus which according to 

 Hatschek 1 ) are innervated by Rami viscerales which correspond to 

 Seitenhornnerven exactly as in Myxine and finally the sensory nerves 

 in Myxine correspond in type to the Rami cutauei (Hatschek) of 

 Amphioxus. To my mind there is no doubt whatsoever that the 

 tentacles of Myxine are the homologues of the oral 

 cirri of Amphioxus. 



The anatomy of Myxinoids has been beautifully described by 

 Müller yet for the purposes of this theory it will be necessary to 

 redescribe in part that of Myxine, to add some slight details and 

 especially to distinguish sharply those parts of the skeleton which 

 are merely ligamentous and those which are formed of the peculiar 

 cartilage. The morphologically first tentacle, to a superficial view the 

 second, is continuous with the unpaired bar of hard tissue which 

 underlies the nasal tube. This bar is the „Knöcherne Stütze der 

 Schnauze V" of Müller and it represents the fused rootpieces of 

 first tentacle. The sensory nerve to this tentacle is a branch of the 

 Ophthalmicus profundus 5"" of Müller 2 ). I term this tentacle the 

 premaxillary tentacle and the rootpiece the premaxillary piece. 



1) Hatschek, Die Metamerie des Amphioxus und des Ammocoetes in 

 „Verhandlungen der Anatomischen Gesellschaft, 1892." Also van Wijhe, 

 Anat. Anz., Bd. VIII. 



2) According to Füebeingee this nerve in Myxine runs under the optic 

 nerve while in Bdellostoma it runs over it and he draws the conclusion 

 that the eye is a later structure than the Trigeminus. 



