Charles J. Chamberlain 13 



In the mosses the centrosome problem has received no serious attention, doubtless 

 on account of the small size of their nuclei. Whether there is even a blepharoplast or 

 not, still remains to be determined. 



In the liverworts, no centrosome is found at any stage in the life-history. How- 

 ever, in Pellia and Conocephalus, and perhaps in all forms with such extensive intra- 

 sporal development of the gametophyte, a centrosphere appears during the early 

 divisions in the germinating spore, but even in these few divisions the centrosphere is 

 very transitory, not persisting from one nuclear division to the next, and appearing 

 only irregularly during the division with which it is concerned. Still, this transitory 

 centrosphere is a functional part of the mitotic figure during the first two or three 

 divisions. In Pellia, at the fourth division, the centrosphere may or may not appear, 

 and in subsequent divisions it was only rarely that we could identify the body at all. 



Among the Thallophytes, sharply defined centrosomes have been described by 

 competent observers who are thoroughly familiar with all phases of the centrosome 

 problem. 



In the fungi, judging from Harper's (16) work on various Ascomycetes, a centro- 

 some is present during the period of free nuclear division in the ascus, when it func- 

 tions in the formation of the spindle. After the period of free nuclear division, the 

 centrosome behaves in a very peculiar manner in forming the young wall of the 

 ascospore. 



The centrosome has received more attention in the algae than in the fungi. In 

 papers by Farmer and Williams (12), and by Strasburger (34), centrosomes are described 

 in the oogonia and segmenting eggs of Fuciis. 



During the early segmentations of the fertilized egg, Strasburger (34) was able to 

 observe the division of the centrosome and to trace its continuity from one cell to 

 another. In the development of the oogonium, however, no such continuity could be 

 recognized. In the large apical cell of Stypocaulon, Swingle (37) found that the 

 centrosome divides, giving rise to the two centrosomes from which the spindle is devel- 

 oped. He was able to recognize the centrosome even during the resting-stage of the 

 nucleus. In the tetraspore mother-cell of Didijota, Mottier (23) found comparatively 

 large and somewhat elongated centrosomes. These bodies divide and, at least during 

 divisions in the tetraspore mother-cell and in the early divisions of the germinating 

 tetraspore, persist from one cell-generation to another. They develop asters and play 

 an important part in the formation of the spindle. 



Lauterborn (21) figures conspicuous centrosomes in Surirella and other diatoms. 

 Karsten (20) also describes centrosomes in diatoms, and his beautiful preparations, 

 which it was our pleasure to examine, show these bodies as sharply defined as in most 

 animal mitoses. Both Lauterborn and Karsten agree that a centrosome, or at least a 

 body derived from it, becomes cylindrical or ring-shaped, and functions as a spindle 

 during mitosis. The centrosomes of diatoms stain intensely and are not surrounded 

 by a centrosphere. Lauterborn found centrosomes even during the resting condition 



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