ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 261 



on the presence of an obvious centrosome, and to the nucleus, so-called, 

 of Protozoa, which is the equivalent of centrosome + nucleus in the 

 metazoan cell, the author gives the name of centromicleus. Such a centro- 

 nucleus may be supposed to have become differentiated into nucleus and 

 extra-nuclear centrosome in higher forms. But it is conceivable that, 

 even after the differentiation of the true centrosome as an independent 

 body, a diffuse cytocentrum may persist in the nucleus, which in such a 

 case would still deserve the name of centronucleus. Such a hypothesis 

 explains the observed phenomenon of regeneration (or better reparation) 

 of a lost centrosome in metazoan cells. The paper concludes with a 

 discussion of terminology ; the more important of the new terms are 

 indicated in the above. 



Development of Ciliated Cells. * — Dr. Alexander Gurwitsch has 

 studied the histogenesis of various types of ciliated epithelial cells, as a 

 means of solving the problem of the function of the different parts of the 

 cell. He finds that the course of development is very different in dif- 

 ferent types of such cells, but in those cases investigated by him (ovi- 

 ducts of rabbit, buccal epithelium of toad and salamander, gut of Lum- 

 bricus), two main types are distinguishable. In the one the nodes of 

 a cytoplasmic reticulum are occupied by corpuscles, which become the 

 basal corpuscles of the cilia, and give rise directly to the cilia. In 

 the second type, the cilia appear before the row of basal corpuscles, 

 which seem to arise secondarily from the cilia themselves. These facts 

 the author believes to be explicable only on the ground that cilia and 

 basal corpuscles are morphologically distinct elements derived from a 

 common substance. He suggests that basal corpuscle and cilium may 

 bear to one another the relation of hair-bulb to hair, but considers that 

 the method of origin excludes the hypothesis that the basal corpuscles 

 are in any sense " kinetic centres." The prime origin of the whole motor 

 apparatus is to be sought in the differentiation from the general cyto- 

 plasm of plasma characterised by its power of movement ; from this 

 mother-substance, which forms a layer at the free margin of the cell, 

 the cilia and related structures are differentiated. 



In another communication^ the author replies to a note by Heiden- 

 hain,| who believes the cells described by Gurwitsch as developing 

 ciliated cells (in the buccal cavity of salamander larvae), to be rather 

 developing mucus cells. Gurwitsch points out the difference as regards 

 position exhibited by mucus cells, and maintains that there is no possi- 

 bility of confusing the two types of cell. 



Central Nervous System of Rabbit.§ — Dr. K. Krause and Dr. M. 

 Phillippson have studied the spinal cord of the rabbit by the aid of intra- 

 venous injection of methylen-blue, and have been able to make out the 

 distribution of the nerve-cells in the anterior horn. The great majority 

 of the cells send neurites into the anterior nerve-roots, and are either 

 polygonal or spindle-shaped. The cell-body is very varied in shape, 

 the shape depending upon the number and arrangement of the dendrites. 



• Arch. Mikr. Anat., lvii. (1901) pp. 184-229 (2 pis.). 



+ Anat. Anzeig., xix. (1901) pp. 44-8 (4 figs.). 



X Cf. this Journal, ante, p. 18. 



§ Arch. Mikr. Anat., lvii. (1901) pp. 488-527 (4 pis.).! 



June 19th, 1901 t 



