STUDÏ OF THE QEXICULA OF CORALLINE. 25 



situated at the distance of aboul out '-third of (lie length of the cells from 

 the upper ends of the cells (tig. 11). In Amp. dilatata the tertiary 

 lamella is remarkable in the part below the pits. This circumstance 

 causes the upper one-third of the cells to stain in a less degree. 

 Hence the longitudial section of the geniculum, after staining, shows 

 alternate parallel carves of faint and deep coloured zones (fig. 5). 



In some cases we find transverse disseptments in the periclinal 

 cells (fig. 6). This character has never been hitherto found in the 

 unizonal genicular cells, as far as the writer could observe. We shall 

 give some account of these dissepments in a later chapter. 



The difference of the property of the cellwall at the genicular and 

 the extragenicular portions is also remarkable in this case. As a rule, 

 the cellwall at the genicular part is thinner than the extragenicular 

 portion. The difference of the thickness occurs abruptly at the point 

 of transition from one to the other. The decrease of thickness is 

 essentially due to the primary cellwall. The middle lamella stains 

 deep with hematoxylin at the genicular part ; the primary cellwall 

 in a less degree and the secondary (sometimes together with the 

 tertiary) lamella stains in intense violet. In the extragenicular 

 portion the middle lamella stains much weaker, and the secondary 

 lamella is almost wanting here (fig. 11). 



I have called it extragenicular portion here. But the area 

 mentioned under the name is somewhat different from the case of the 

 unizonal o-eniculum. As mio-ht be well understood from the structure 



O O 



of the genicula under treatment, there is no special portion which 

 corresponds to the extragenicular portion of the unizonal genicula. 

 The parts in contact with the articular portion, from the morphological 

 point of view, have no special differentiation. A part, however, of 

 each cell just related to the genicular portion is destitute of starch 

 grains. The nourishment is probably consumed during the formation 



