RAND: NERVOUS SYSTEM OF LUMBRICID^. 97 



area Solger suggests to be "das Centralkorperchen oder die Sphere 

 attractive im Ganzeu oder ein Theil derselbeu." 



Kolliker ('89) found the attraction sphere in cleavage cells of Sire- 

 don while the nucleus was in the resting condition. 



Burger ('91) found an attraction sphere with centrosome and radia- 

 tions in the cells of the body fluid of nemertines. 



Flemming ('91, '91', '91'') described " die strahligen Spharen und 

 ihre Centralkorper " in resting leucocytes of the salamander. In the 

 amitotic divisions of the nuclei of these cells the sphere does not divide, 

 but Flemming believes that it exerts some influence over the amitotic 

 process, since " bei den Abschnlirungen die Sphare eben nicht einer 

 beliebigen Stelle der Kernmasse benachbart liegt, soudem grade an 

 den Abschnlirungsbriicken " ('91* p. 285). The centrosome was also 

 found in the resting cells of the lung epithelium and in the flat con- 

 nective-tissue cells and endothelial cells of the peritoneum of the sala- 

 mander larva, but in these fixed cells no radiations could be seen. The 

 " Centralkorper " generally consisted of two minute granules lying close 

 together in the cytoplasm very near the nuclear membrane. Often a 

 dark band could be seen connecting the two granules. When the 

 nucleus was approaching the spireme condition the centrosomes were 

 farther apart and this dark band was more conspicuous. Flemming 

 therefore believed it to be "die erste Bildungsanlage der Spindel." 



Flemming's discovery, made on leucocytes of the salamander, was 

 corroborated by Heidenhain (91), who also found the centrosome and 

 sphere in the cells of the bone-marrow of young rabbits, as well as in 

 pathological epithelium from human lungs and in some leucocytes from 

 the same human material. 



Henneguy ('91) showed the continuity of the attraction spheres in the 

 developing trout egg. 



Hermann ('91) found an " Archoplasmastrahlung " in resting sperma- 

 togonia of the frog, and resting spermatocytes of Helix pomatia. In 

 resting spermatocytes of Proteus he describes an archoplasm with a 

 conspicuous central granule. 



Meves ('91) described amitosis in the spermatogonia of the salaman- 

 der. During the dividing of the nucleus the " attraction sphere " took 

 the form of a ring about the region of constriction. 



Solger ('91) described an attraction sphere in resting chromatophores 

 of teleosts. 



Heidenhain ('92) observed, in two cases of leucocytes with two nuclei, 

 two spheres present, with a well-developed spindle formed between them. 



