218 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



quantity of protoplasm belonging to them. . . . These cells are arranged 

 in rows, or in single files radiating from the upper and inner angle of 

 the fornix ; each row is separated from its neighbors by bundles of 

 fibrillae, which also radiate from the same point ; these bundles are 

 thicker at the proximal end, and gradually become smaller by giving 

 off radiating fibrils in their course. The cells are attached to these 

 fibrils sometimes by short branchlets, and sometimes they are sessile." 



Stieda ('68), Bellonci ('80, '81, '82), Mayser ('82), Wright ('84), 

 Auerbach ('88), and C. L. Herrick ('91, '92, '92*) treat of the optic 

 lobes, but have little or nothing to say of the torus, and nothing what- 

 ever of its finer structure. Of the more recent writers treating of this 

 region, the torus longitudinalis is not mentioned by Fusari ('87), 

 Burckhardt ('94), Van Gehuchten ('94), Neumeyer ('95), Mirto ('95), 

 Haller ('98), or Pedaschenko (:01), and receives mere mention from 

 Ramsey (:0l). 



Rabl-Ruckhard ('82, '84), from embryological and comparative ana- 

 tomical studies, proved Fritsch to be in error, and showed the torus 

 longitudinalis to be a structure peculiar to fishes. Later ('87), in study- 

 ing the development of the torus in the salmon, he found it to be 

 developed from the roof of the mesencephalon as a longitudinal thicken- 

 ing, by the multiplication of the cells of the inner layer of the tectum 

 opticum. He believed the torus longitudinalis to be represented in the 

 higher vertebrates by the thickened ependyma which he observed under 

 the posterior commissure in amphibia, reptiles, and birds. In a later 

 paper Rabl-Riickhard ('94) again emphasized this view. This erro- 

 neous interpretation has been accepted by Gage ('93) and Johnston 

 (:01, :03), and has led to considerable confusion. The cells described 

 by Johnston (.Ol, pp. 48, 145) as "Type C: cells of the torus longitu- 

 dinalis Halleri," are more properly cells of the tectum opticum. 



C. L. Herrick ('91, p. 172) says of the torus merely: "The structure 

 of this body is very simple, consisting of dense clusters of small cells 

 like Deiter's corpuscles." In common with previous observers he did 

 not consider the torus a nervous centre. In a later paper ('92, p. 44), 

 he says : " A considerable part of the fibres which enter the torus 

 longitudinalis are not nerve-fibres, but arise from the modified epithelium 

 of that body and pass to the ectal surface of the tectum. Such gelatinous 

 tracts are to be regarded as mere persistent walls of the original single 

 epithelium." 



Sala ('95) studied the torus longitudinalis of the young of Tinea 

 vulgaris by tlie method of Golgi, and demonstrated the presence of 



