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Pig. 9. Lophius piscalorius. 



pole of the radix spinalis trigemini, from which it can no longer be 

 distinguished in the more caudal planes. 



In Teleostei, especially lophius piscatorius, the case is more simple. 

 The radix mesencephalica is less compact here; it is formed by 

 several, 4 or 5, thin, medullary bundles, from which, at the point 



where the sens, trigem. root enters, 

 only loosel}" connected fibres 

 separate, to leave the oblongata 

 dorsally from the entering sens, 

 nerve or between the most dorsal 

 fibres. Several (4) sections further 

 distally the nerv. V mot. cilso 

 leaves the brain stem ; this too 

 passes into the dorsal part of 

 the here entering sens. V fibres, 

 still ventrally to the mesenc. 

 quintus, and clearly separate from 

 it (fig. 9). Further caudally no- 

 thing more is to be found of 

 the radix mesencephalica. 

 Amphibia. x\ccording to Pedro Ramon (I.e.) the cells of origin of 

 the mesenc. quintus of these animals lie in the tectum opticum, 

 close to the ependyma of the ventr. lob. opt., somewhat scattered 

 laterally to and even round the vent. lob. opt. ; thus in this respect 

 they rather resemble the condition in teleostei. 



The root-fibres run in the usual way distally, the majority of them 

 first turn towards the periphery in a cross plane where the trigeminus 

 already enters. Here they remain ventral, and are accompanied in 

 their turn by the motor V root, from which they are clearly sepa- 

 rated {rana fig. 10). A small remnant of the radix mesencephalica 

 proceeds caudally, on the same relative place as in scyllium, and 

 can soon no longer be distinguished. 



Reptilia. Here, as regards the position of the elements of the 

 large-celled nucleus tecti different conditions are met with in repre- 

 sentatives of the lacertilia, ophidia, crocodilidae, chelonidae, which 

 without doubt are connected with the general structure of the 

 tectum opticum of the animals, especially in so far as this is 

 influenced by the torus semicircular is intruding lower down at 

 the back of the ventricle, especially in the crocodilidae. Fig. 11 

 gives an idea of this, and shows on a cross section the arrangement 

 of the mesenc. quintus cells in alligator sclerops. A few cells lie in 

 the ependyma layers which surround the ventricle. The majority 



