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adjoining the area vestibulo-lateralis, I found that the vestibularis 
nuclei play an important part in the development of the cerebellar 
nuclei. 
Hitherto a comparative study of the cerebellar nuclei has never 
been extended to the lower vertebrata; some of these nuclei were 
even unknown in the lower animals. Nevertheless it appears that 
the nuclei cerebelli in the different classes of vertebrates exhibit a 
fairly regular course of development in form, extent and position. 
My research was made chiefly among the lower vertebrata, viz. 
Petromyzon, some sharks and some reptiles. For the amphibians I 
may refer to Herrick’). In the birds, which I also studied, I found 
conditions which have already been described by BraNpis®), CaJaL*) 
and Sximazono*), who agree in the main with each other. I merely 
give a sketch of a bird to facilitate a survey. 
The aspect of the nuclei cerebelli of mammals has often been 
illustrated, and I may assume it to be sufficiently well known. In 
the lowest order of mammals that 1 was able to examine, some 
marsupials, I found the nuclei cerebelli already highly developed, but 
slightly different in essentials from those of the higher mammals. 
The size of the nucleus dentatus, for instance, may differ greatly 
and to a certain degree be independent of the development of the 
hemispheres, but the cerebellar nuclei are in principle fairly alike 
in all mammals, at least as far as they may be compared with those of 
the other vertebrate orders. I need not therefore give here a separate 
description or reproduction of these nuclei in the mammals. 
Petromyzon fluviatilis. 
The cerebellum of Petromyzon, which is found immediately orally 
of the area vestibulo-lateralis, is not much more that a thin plate. 
Though consisting chiefly of fibres, cells are also to be found scattered 
in it, as was first described by Scrarer®). These are granular-cells 
and a few large cells which, according to him, JOHNSTON and SCHILLING °) 
1) C. Jupson Herrick: The cerebellum of necturus and other urodele amphibia. 
The Journal of compar. Neurol. Feb. 1914. 
2) Branpis: Untersuchungen über das Gehirn der Vögel. Arch. f. mikrosk. Anat. 
Bd. 43, Vol. (1894). 
3) GAJAL: Los ganglios centrales del cerebello de los aves. Trabajos det labo- 
ratorio de Madrid. Vol. VI. 
4) Suimazono: Das Kleinhirn der Végel. Archiv. f. mikrosk. Anat. 80 Vol. (1912). 
5) Scuarer, Zur Histologie des Kleinhirns bei Petromyzon, An. Anz. Vol. 16. 
6) Scumune, Ueber das Gehirn von Petromyzon fluviatilis, 1907, Abh. der 
Senckenberg Naturforschende Gesellschaft. 
