296 



Thev were however mure com pact than those of Tgast, and inclosed 

 t^rains of sand conkl only be discovcretl at the outer side. In con- 

 sequence of this fact an enormous difference presents itself between 

 the microscopic character. As becomes immediately apparent from 

 the figure above the slag is characterized by an excellent ophitic 

 structnre. The secreting products consist chiefly of more or less 

 allongated phenocrysts of plagioclase varying in length between 0.05 

 and 0.6 mm. and in breadth between 0.01 and 0,04 mm. According 

 to the extinction-direction this plagioclase belongs to labradorite. The 

 intervening metastasis (in the figure black) consists of a globulitic 

 glass, in which are found numerous magnetite crystals surrountled 

 by a light halo. They are single octaeders of which the smaller 

 ones are sometimes arranged in lines. Locally there are in the base 

 still aygite individuals and very narrow plagioclase slags. 

 The origin of this slag could not be ascertained. 



Anatomy. — ^'Contributions upon N'eurobio taxis." {The arrangement 

 of the motor nuclei in Myxine glutinosa in Cryptobranchus 

 Necturus, Rana fusca and Bufo). (From the Anatomical Institute 

 in Berlin and the Institute for Brainresearch, Amsterdam)^). 

 By Dr. P. Röthig; Berlin. (Communicated by Prof. L. Bolk). 



Myxine glutinosa '). 



It is known (Anders Retzius, Johannes Muller, Gustaf Retzius, 

 L. Edinger et. al.) that the brain of Myxine glutinosa is very rudi- 

 mentary. Some parts of it are compressed in a f ron to-caudal, others 

 in a caudo-frontal direction. 



The study of complete frontal, horizontal and sagittal sectioJis 

 reveals — as far as the mixed and motor nerveroots are concerned — 

 the presence of the Trigeminus, Facialis and several (occipito-) spinal 

 nerves. On the contrary there is no Oculomotorius, no Trochlears, no 

 Abducens and no Glossopharyngeus. Also Gustaf Retzius') — in his 



1) My sojourn in the Institute for Brainresearch in Amsterdam has been faci- 

 litated by a gift from the Preussische Akademie der Wissenschaften for which I 

 want to express my thanks. 



~) The specimens of Myxine glutinosa used for this research have been collected 

 in Krislineberg in Sweden. They were fixed while still living and stained after 

 various methods, chiefly after Bielchowsky They will also be used for a monograph 

 which I intend to publish together with Dr Artrns Kappers (Amsterdam) on 

 the central nervous system of this animal. 



^) Rktzius, Biologische Untersuchungen N. V. Bnd. V 1893, (Das Gehirn und 

 Auge von Myxine.) 



