The finer Anatomy of the Nervous System of Myxine glutinosa. 373 



encephalon and Mesencej)halon the Ganglia habenulae are found 

 projecting dorsally (Fig. 5 G.h.d and GJi.s), the left ganglion being 

 partly situated in an anterior position to the right; they are elon- 

 gated in horizontal section and have probably obtained their peculiar 

 relative position and elongated form by lack of space inside the 

 capsule during the late development of the brain. Those parts of 

 the ganglia which project into the brain are in too close contact 

 with each other for any separating space to be shown between them. 



In horizontal section the ganglion shows a rhomboidal shape 

 (Fig. 6 and 7j, in transverse, that of a wedge, point downwards. This 

 ganglion has already been described by A. Retzius (36) as a round, 

 single body and he identifies it with Glandula pinealis; Sanders 

 (41) likewise describes this formation as single, but G. Retzius (38) 

 has recognised its duplex nature. Like Retzius, I have not been 

 able to find any sign of Epiphysis or the strings which project from 

 the ganglion as in Petromyzon. 



The olfactory lobe shows the same arrangement as that found 

 in higher animals. Retzius succeeded in following the olfactory 

 fibre into the characteristic glomeruli in Golgi preparations and my 

 results with Iron-haematoxylin preparations confirm this view. These 

 olfactory glomeruli are studded over the rostral surface of the brain 

 in a thin layer generally two or three thick. In horizontal sections 

 they commence to be visible dorsally along the rostral part of the 

 fissure that separates the olfactory lobes (Fig. 5 and 6) and disap- 

 pear from the following sections for some time (Fig. 7), but in the 

 lower half of the frontal surface they reappear and are found in 

 ventral direction below the Trigoneum cinereum. 



In a horizontal section of the Bulbus olfactorius we recognise 

 diff'erent strata; — rostrally the stratum of the Fila olfactoria, then 

 the Stratum glomerulorum and thirdly the Stratum griseum. This 

 stratum is subdivided into two different strata in the higher animals, 

 the Stratum moleculare and the Stratum of the mitral cells, but in 

 Myxine it is impossible to find any subdivison, the mitral cells 

 being close to the Stratum glomerulorum. Besides these strata there 

 is described a fourth one in the higher animals, the Stratum of the 

 medullary fibres. In Myxine no medullary fibres exist of course, 

 but in the same })osition we find a layer of non-medullated fibres 

 containing the olftictory tracts, separating the gray matter of the 

 olfactory lobe from that of the next division of the brain, and, 

 considering the same analogous to the stratum of the medullary 



