288 C. U. Ariens Kappers 



Though small at first and absorbing but little of the optic tract, or of 

 its coUaterals, this centre gradually grows in size, during phylogenesis, 

 receiving more and more ootic fibers until at last in man, the greater 

 part of this nerve ends in it. The way in which this nucleus starts 

 its development in the lamprey, was investigated by the above-named 

 authors. 



In the lamprey, which before seemed to lack a corpus geniculatum, 

 a group of cells was discovered, not yet in a lateral position, but showing 

 a strongly peripheral outgrowth of their dendrites, thus gaining contact 

 with collaterals, proceeding from the optic tract Juring its course on the 

 lateral wall of the thalamus. Though this may not be called a lateral 

 geniculate «nucleus*, yet it is a pronounced dendritic contact of medial 

 thalamic cells, with the optic tract. The further development of these 

 cells to a lateral geniculate nucleus, evidently is effected in the same way 

 as with the nuclei of the oblongata, the cell-bodies following later on the 

 dendrites, until a nucleus has been formed lying cióse to the optic tract. 

 So we have here a new and wel'-studied case of neurobiotaxis in a part of 

 the optic system. Till now we are not able to explain the factors that 

 make this nucleus to become the chief centre of the opticus in higher 

 vertebrates. The fact, demonstrated experimentally in fishes by Zeeman 

 Lubsen, that chisfly fibers of the fundus oculi, viz, those corresponding- 

 with the frontal área of visión, are connected with the geniculatum 

 points to the probability that already in these animáis the geniculate 

 body has to do with finer discrimination (here for feeding purposes) which 

 salso rendered evident by the fact that in man (Ronne) such a large part 

 oí its fibers come from the macula. 



Further it in generally known that in mammals the cortical projection 

 proceeds from the corpus geniculatum laterale, not from the roof of the 

 mid-brain, but we are as yet ignorant of the special reason why this pro- 

 jection starts from this nucleus instead from the roof of the mid-brain. 

 Probably it is owing to the fact of the geniculatum laterale being associated 

 indirectly with other thalamic centres (perhaps of a finer stereognostic 

 nature). By this association a correlate to existing forebrain correlations 

 might be present in the outer geniculate nucleus, thus causing its associa- 

 tion with the cortex. But this is merely a supposition. It was however 

 evident to me from the very beginning of my researches, and it may be 

 empíiasized here, that there always is a peculiar selection, in all these phe- 



