motor fibres in the facial nerve of the American Myxinoid Bdelio- 

 stoma dombeyi. 



After Jon. Muller, Gustaf Retzius ^) gave very valuable contri- 

 butions which appeared abundantly illustrated in 1881 and J 893. 

 It is just the excellent descriptions given by G. Retzius that show 

 how difficult the interpretation of this bi-ain is, for G. Retzius himself 

 emphasizes at the end of his elaborate desQi-iption of 1893 (p. 63) 

 that — though he had been gathering the data concerning the 

 brain of this animal for several years, he had not yet succeeded in 

 obtaining a complete idea of its exact relations. 



G. Retzius mentions, as did P. RöTniG in his contribution (1. c), 

 the absence of the trochlearis, oculoniolorius and abducens. The 

 most frontal nerve roots, according to him, are two trigeminal 

 branches (p. 60 and Table 24, F.'g. 1 — 3) each provided with a 

 spindleshaped ganglion. 



Following on this he tinds a small nerve without ganglion (a 

 motor nerve consequently) which he considers to be — like Joh. 

 Muller — the facial nerve. Close to this nerve he tinds a third 

 ganglionated root, which he supposes to be a third trigeminut; root; 

 and behind these the two roots of the octavus occur which he had 

 already described before (1881) : the Ramus anterior and r.imus 

 posterior acustici. Much more backward the vagus roots appear 

 without ganglion. Dorsally from these he, however, iinds a small 

 sensory root with an oval ganglion, which he considers to be a 

 sensory vagus root (p. 59), 



After G. Retzius Sanders ') took up this subject. Since this work 

 was not available for us, we can only quote from it what Holm 

 has cited (1. c. infra). 



According to this author Sanders found the V, VII, Vlll and X 

 nerves, but differs in so far from G. Retzius that he considers some 

 roots entering the brain behind the vagus of Retzius still as vagus 

 roots, whilst the latter mentions them as spino-occipital nerves. 



It is Sanders' merit to have first given a detailed description of 

 the oblongata-miclei, which he divides into two cellgroups of which 

 one has an entirely central position near the dorsal raphe: "ganglia 

 centralia", and another near the perifery of the bulb: "ganglia latero- 



5) G. Retzius. Das Gehörorgan d. Wirl-eltiere Bd. I, Stockholm, 1881 ; Ueb. d. 

 Hypophyse von Myxine Biolog. Untersuclig. Bd. VI ; Das Riickenmark von Myxine 

 Biolog. Untersuclig. N. F. Bd. W. 1891 ; Das Geliirn und das Auge von Myxine 

 Biolog, Untersuchg, N. F, Bd. V 1893. 



") Sanders. Researches on the nervous system of Myxine glulinosa. 1894, 

 Williams and Norgale, London. 



1* 



