A STUDY OF THE GENICULA OP COKALLINjE. 13 



a knotty protuberance is found at the point of insertion of the 

 geniculum into the articulas. In Amp. canaliculata, Mart, the genicula 



are always directly attached to the margins of the articulus, that is to 

 say, the genicula grow from the margins without any protuberance 

 or prolongation of the calcified portion. 



In most cases the abnormal genicula seem to have generated from 

 the cortex. Im Amp. cretacea, a number of the cortical cells increase 

 layer upon layer at a certain portion of the surface of an articulus in 

 such a degree as to produce a wart-like protuberance. One of the 

 cellular layers elongates to an extraordinary degree, in like manner as 

 a normal genicular formation, and thus the primary geniculum is 

 built up. 



Some of the branches of Amp. cretacea, Amp. valonioides, etc. 

 originate from the cortex in the manner just described above. In 

 Amp. aspergillum the primary genicula of the pinnules are always 

 generated from the cortex. These ramules are by no means abnormal 

 branches in these species, but a characteristic mode of ramification 

 limited to them. 



Thus the genicula at the distal end of an articulus which give 

 rise to dichotomy, trichotomy, whorly or pinnation (not of Amp,, 

 aspergillum) are originated from the medulla ; and those of the lateral 

 branches or processes are mostly from the cortex. The abnormal 

 genicula generally belong to the latter category. 



RELATIVE POSITION OF THE GENICULAR AND THE 

 ARTICULAR CELLS. 



The structure of the articuli of the Corallinœ may be easily divided 

 into two portions. The internal part is constructed with long 

 filamentous cells bound together along the periclinal side of the cells. 

 These cells occupy the greater part of the diameter. The cells at the 



