1384 Journal of Applied Microscopy 



Gurwitsch's part the circumstance that " the epithelium of the esophagus and 

 stomach in the transition region may not be sharply distinct from each other, so 

 that ciliated regions could be found in the surface epithelium." This is impos- 

 sible ; since the part of the epithelium which was used for investigation lay above 

 the esophagus, and since the whole region was covered with a similar unbroken 

 coat of these questioned cells, just as in later life the ciliated coat is entirely 

 unbroken, the author's conclusion is again justified and Heidenhain's assump- 

 tion would only be right if there were ground for the belief that the whole 

 pharyngeal epithelium was changed to a mucous condition and that later ciliated 

 epithelium arose dc novo from some unknown source. No evidence exists for 

 this and such a process could not easily escape notice. Moreover, if Heiden- 

 hain's explanation were applied to all these questioned cells, then this rodded 

 border, which occurs in so many forms and kinds of cells, must be declared the 

 forerunner of mucoid formation on the ground alone that it seems to be the case 

 in this one kind of cell. 



It cannot be doubted that identical tissues in two nearly related species of 

 animals have in similar developmental stages an 'entirely different appearance. 

 Therefore it is no objection to the writer's hypothesis that the methods of 

 development of ciliated cells in salamanders may differ in various cases. The 

 only apparent question existing is whether these steps are those of ciliary or 

 mucoid formation in the cells. 



The facts important for histogenesis in general must satisfy us that similar 

 structures may owe their origin to different methods of development, and that 

 the histogenetic processes which are found in one species may not be applied 

 to a nearly related one. This is also true in other lines, as for example, the his- 

 togenesis of crystalline lens in different animals and the ectodermal origin of 

 cartilage in Petromyzon. 



The author adds a few words on the beaker cells in the same epithelium. 

 This in the salamandar larva has always two layers, the one with the peculiar rod- 

 cells is set on a layer of cubical or more or less sloping cells. In not a single 

 case was the first or rodded layer found in contact with the basilar membranes. 

 On the other hand, all the mucous cells, independent of their condition of func- 

 tion, were placed directly on the basilar membrane. This immediately suggested 

 the latter to be the mother cells of the beaker cells. While this could not be 

 maintained by direct evidence, not sufficient transitional stages being examined, 

 it is enough for this argument to state the facts that there is a good criterion for 

 the differentiation of the immature mucous cell from the rod cell. " Thus the 

 beaker or goblet mucous cells of the pharyngeal epithelium point clearly to a layer 

 underlying the latter ciliated cells.) This relation holds true in all cases and all 

 stages in development. e. j. c. 



