14 ART. 14.-K. YENDO: 



middle portion run in the direction of the axis of the articulas. Those 

 at the peripheral portion more and more become inclined, diminishing, 

 at the same time, in the length, until they result in globular or cubical 

 cells running radially to form the cortex. The medullary cells are 

 mostly arranged in zones. These zones are easily observable when 

 the calcium carbonate in the frond has been dissolved. They appear 

 as concentric parallel lines, convex toward the apex of the frond 

 (figg. 3, 5, 6). 



A geniculum is built up with one or more zones of the periclinal 

 cells. The majority of the* Corallinœ belong to the former category. 

 In the case when one zone of the periclinal cells shared the formation 

 of geniculum, the middle portions of the cells serve as the geniculum 

 proper. Both ends of the cells have the deposit of calcium carbonate 

 and have no proper function as genicular cells. The calcified distal 

 ends should for the sake of convenience be called the extra-erenicular 



o 



portion (figg. 9-10). 



The bordering line between the articuli and both ends of a 

 geniculum varies more or less according to the species. As has been 

 mentioned above, a geniculum is not built up by the mass of the entire 

 cell but by a mass of parts of the cells. In other words, the cells at 

 the critical portion which divide a geniculum and an articulus are 

 separated into two parts, the one serving to build the geniculum and 

 the other the articulus (figg. 1, 2, 4). Hence the word '•borders" 

 does not apply to the continuation of the cell boundaries. It 

 means the continuity of the transitional points of the genicular and 

 the articular portions of the cells ; or the critical points of the genicular 

 and the extragenicular portions. 



In the hair-like Jania the number of the genicular cells is much 

 less than that of the robust forms, and they are arranged in a less 

 regular manner. Generally speaking, the cells at the middle portion 



