96 bulletin: museum of comparative zoology, 



of some of the deeply stained fibres that happened to lie at the centre 

 of the spiral figure. 



Kolster ('00) gives a brief preliminary account of centrosomes in 

 the nerve cells of Cuttus scorpius. The only two figures given repre- 

 sent one or two deeply stained granules surrounded by a small clear area 

 and lying near the cell centre, the nuclei being excentric and concave 

 on the side toward the cell centre. 



2. The Centrosome in Other Resting Cells. 



Leaving nerve cells and turning now to the question of the centro- 

 some in other resting cells, and especially in tissue cells, a considerable 

 literature on this subject is found to have grown up during the last ten 

 years. Previous to 1889 no accurate description had been given of a 

 centrosome and sphere in resting tissue cells, but doubtless many of the 

 descriptions of "Nebenkerne" and " Central massen " refer to struc- 

 tures that would now be recognized as centrosomes or spheres. 



Van Beneden et Neyt ('87, p. 279) found that the attraction sphere 

 persisted during the resting periods of the early cleavages of Ascaris. 

 " Nous sommes done autorises a penser que la sphere attractive avec 

 son corpuscule central constitue un organe permanent, non seulement 

 pour les premiers blastoraeres, mais pour toute cellule ; qu'elle constitue 

 un organe de la cellule au meme titre que le noyau lui-meme ; que tout 

 corpuscule central derive d'un corpuscule anterieur; que toute sphere 

 precede d'une sphere anterieui*e, et que la division de la spliere precede 

 celle du noyau cellulaire." 



Boveri ('88) showed the continuity of the centrosome in the cleavage 

 of Ascaris, and set forth his conception of a specific " archoplasm," which 

 is strewn through the cell in granular form during the resting period, 

 and, in mitosis, collects about the centrosomes to give rise to the radi- 

 ating systems. 



Eabl ('89) observed that the resting nuclei of epithelial cells in 

 Triton were indented upon one side, while in the cytoplasm, in the 

 region of the indentation, was a highly refractive homogeneous mass 

 which, he suggested, was due to the presence of the " Polkorperchen " 

 or the " Attractionssphare." 



Solger ('89, '90) found a radiating structure in the pigment cells of 

 some teleosts. The cells frequently have two nuclei which are situated 

 at the cell centre, and between them is a small clear area, from which 

 proceed radiating lines of granules toward the periphery. The central 



