492 E. A. MTNCHIN. 



monaxon spicules, and these, when present, vary very much in 

 size and number. To Bidder, however, belongs the credit of 

 having been the first to recognise the true nature of these cells 

 as contracted pores. In addition to the species already enume- 

 rated, I can vouch for their occurrence in b 1 an ca, cerebrum, 

 reticulum, contorta, and ^'Clathrina, sp. dub.,^^ and 

 since in all these species the pores have similar characteristics 

 and contract in the same way, I have but little doubt these 

 usually very conspicuous cells — '^ Kornerzellen," '' cellules 

 spheruleuses," "yellow granules," as they have been so variously 

 termed — will be found in any species of Clathrina where they 

 are sought for under suitable conditions. 



Origin of the Porocytes. — We have now considered in 

 some detail the structure and appearance of the pore-cells, both 

 when expanded and functioning as pores, and in the contracted 

 condition in which they most often figure in the literature. 

 The porocytes do not, however, form a separate layer, growing 

 and multiplying amongst themselves, but each porocyte arises 

 separately and independently from the dermal flat epithelium. I 

 have already described in a former communication (1892 [3]) the 

 more usual method by which the pores arise, either at any point 

 during the general growth and increase in size of the tubes or 

 at the ends of the blind diverticula, namely, by immigration of 

 a cell of the flat epithelium. Without going fully into the 

 matter at present, I will merely refer to PI. 39^ figs. 15 and 

 16, por. c, which represent two of these future porocytes, 

 in process of immigration. It will be seen that the cells in 

 question only diff'er from the rest of the flat epithelium in 

 their larger size and more numerous granules, and in the 

 possession of rather larger nuclei. Each cell shows a portion 

 still on the surface, and therefore visible at the higher focus, 

 which has the granules spread out, and is without definite 

 limits, and a deeper portion, visible at a lower focus, which 

 has already come into contact with the collar- cells, and in 

 consequence has a sharp outline showing the characteristic 

 bays and points. My reason for figuring these two cells is 

 that they show a feature often to be observed, namely, the 



