278 The Microscope. 



it is composed of exceedingly fine fibres radiating in every direc- 

 tion from the centre toward the cell wall and forming meshes 

 so narrow that they are very inconspicuous, really demanding 

 somewhat careful search to see them. Here the fibrillated 

 structure dominates, and this appearance calls to mind the 

 aspect of an almanac sun, the ftice of the symbol being here 

 represented by the somewhat irregular nucleus, and with the 

 fine rays increased to an indefinite number. 



While examining these large and beautiful cells, the observer 

 should bear in mind these two appearances, and not be dis- 

 turbed if the network is not as plainly visible and the meshes as 

 close, small and regular as he expected they would be. In my 

 experience the fibrils are the most readily demonstrated, unless 

 a very high power, a 1-12 or higher, be used to study the pro- 

 toplasm surrounding the tubule of the nucleus and situated 

 between it and the membrane enclosing the nucleus and separat- 

 ing it from the protoplasmic contents of the cell. In this part 

 of the object the reticulum, or network of delicate fibres, is 

 superbly demonstrable. 



Those that have been reading Professor Kirsch's papers on 

 Cytology have learned that the nucleus, while it appears to be 

 formed of a reticulation or network, is in reality composed of a 

 single fine tubule much convoluted upon itself, the apparent net- 

 work being produced by the crossing of the tubule over its pre- 

 ceding convolutions. The nucleus is in structure only a single, 

 very much twisted tube, whose hollow is filled with a substance 

 that has been named the nuclein. In the intestinal cells of 

 Oniscus beautiful optical sections of this are obtainable, since 

 the nuclein takes the stain with great avidity. The network is 

 here conspicuous and the meshes, unlike those of the protoplasm 

 of the cell, are fine and small. Altogether, therefore, the intes- 

 tinal cells of this common animal cannot be excelled as objects 

 in which to examine the structure of the protoplasm, a subject 

 that is always interesting and should be seen and understood by 

 every microscopist. 



Acknowledgment — To Dr. W. N. Beggs, St. Louis, for a 

 superb preparation of pigeon's blood preserved by the osmic 

 acid method and mounted in glycerine. Dr. Beggs is one of 

 the most accomplished and expert preparers of histological 



