rand: nervous system of LUMBRICIDiE. 101 



assimilation of food, and taking their place as blood elements, equal 

 in importance to the erythrocytes and leucocytes" (p. 13). 



Von Lenhossek ('98), in studying the development of the sperma- 

 tozoa of the rat, found the flagellum to he a product of the centrosorae. 

 In another paper ('98*) he described the centrosomes and " Basalkor- 

 perchen " in the cells of ciliated epithelium. In cells that did not bear 

 cilia, the microcentre was present, lying at the extreme outer end of the 

 columnar cell. In the ciliated cells no microcentres were found, but 

 there was a layer of granules just beneath the eiliated surface of the 

 cell, the number of granules corresponding closely with the number of 

 cilia. Von Lenhossek gives the name of " Basalkorperchen " to these 

 granules, and thinks they are homologous with the microcentre of the 

 non-ciliated cells. 



Zimmermann ('98) discusses the centrosome in epithelial and gland 

 cells of mammals, including man. He points out that, as in mitosis 

 the centrosome is the centre of motor processes, so in resting cells the 

 centrosome is always located at the centre of activity. If there is an 

 equal degree of activity throughout the cell, the centrosome is at the 

 centre of the cell, unless displaced by a large nucleus (leucocytes, pig- 

 ment cells, non-striated muscle cells). In gland cells, it is at the centre 

 of secretory activity. In ciliated cells and epithelial cells with pseu- 

 dopodial processes, the microcentre is close to the outer end of the cell. 

 Where there is a single flagellum, as in the spermatozoon, the centro- 

 some is at the point where the flagellum enters the cell. He says 

 (p. 697) : " Ich glaube . . . dass, ganz allgemein gesprochen, das ^likro- 

 centrum das motorische Centrum, also das ' Kinocentrum ' der Zelle sei 

 (gegeniiber dem Kern als ' Chemoceutrum ')." 



Von Lenhossek ('99) describes a microcentre, in the sense of Heiden- 

 hain, in the non-striated muscle cells of the cat. As non-striated muscle 

 cells are known to divide by mitosis in cases of regeneration, we should 

 expect to find the microcentre in the resting cell. 



Among other authors who have described centrosomes in resting cells 

 may be mentioned Hansemann ('91, '93 ; cells of human brain tumor, 

 cancer cells, human leucocytes, mesenterial connective tissue of young 

 cats and rabbits) ; Guignard ('91, '97 ; plant cells) ; Eismond ('94 ; 

 cleavage cells of Triton tseniatus and Siredon) ; Zimmermann ('94 ; 

 human epithelium, stroma cells of cat ovary) ; de Bruyne ('95 ; con- 

 nective-tissue cells) ; Meves ('95 ; spermatogonia of salamander ; '95' ; 

 sesamoid cartilage cells in the tendon achilles of the frog) ; Moore 

 ('95; sperm cells of elasmobranchs) ; Rawitz ('95; sperm cells of sala- 



