440 M. J. Brock on the 



being pretty uniformly distributed over the most elevated 

 part of the wart. Exceptionally a flask-shaped organ occurs 

 on the outer declivity of the crescentiform furrow, therefore 

 really outside the domain of the wart itself. The " flask- 

 shaped organs," as we will name them for the present, 

 usually stand in groups of two or three close together, but 

 not unfrequently singly. Their size varies little. I found 

 the greatest long diameter of a well-developed organ to be 0'2 

 millim., while the greatest transverse diameter amounted to 

 0"15 millim. This would be sufficient to enable them to be 

 recognized under the lens even in a fresh torn preparation, 

 that is to say, supposing them to be sufiiciently differentiated 

 from the surrounding tissue, which I greatly doubt. 



The minute structure of a flask-shaped organ is compara- 

 tively simple. The whole is surrounded by a thin membrane, 

 visible in sections as a strong contour, and which here and 

 there contains imbedded fusiform nuclei. The chief contents 

 consist of large cells, which in life are probably nearly round, 

 but in my preparations irregularly polygonal, in consequence 

 of the shrivelling, which cannot quite be avoided. These 

 cells also possess a distinct membrane, recognizable as a thick 

 contour ; their protoplasm is quite free from granular inclu- 

 sions, and in life probably perfectly transparent and strongly 

 refractive. In my chromic-acid and osmium preparations it 

 had acquired a finely reticular character, no doubt a pheno- 

 menon of coagulation ; while in the alcoholic preparations a 

 dully-lustrous fat-like substance had separated in large drops. 

 The remarkably small, perfectly spherical nucleus is placed 

 quite excentrically on a part of the membrane. The greatest 

 diameter of these " transparent cells " is 15-25 /a, that of 

 their nuclei 3-5 fju. 



These transparent cells are surrounded, like a nut by its 

 shell, by a somewhat differently constituted layer, which 

 extends directly inwards from the external limiting mem- 

 brane. This '' external layer " is most perfectly developed 

 at the bottom of the bellied part of the flask-shaped organ 

 (which lies away from the surface of the mantle), and thence 

 advances forwards, but without ever attaining the fore- 

 most part, that is to say, to keep up the comparison, the 

 mouth of the flask. On the whole, this cell-layer is charac- 

 terized by great irregularity. Not only do the individual 

 cell-elements composing it often project irregularly into the 

 cavity of the flask, but their arrangement is also sometimes 

 interrupted ; there occur in it larger and smaller gaps, into 

 which the transparent cells penetrate and thus come into direct 

 contact with the limiting membrane. In contrast to the 



