STUDY OF THE GRAPTOLITES. 



193 



the better-preserved specimens, that there is a slender common canal at the 

 base of each range of cellules. These several canals may or may not 

 communicate with each other.* 



3. The Calydes or Cellules: their form and mode of development. — Since 

 a large proportion of the specimens of graptolites which come under our 

 observation for the purposes of study or otherwise, are fragmentary, it 

 becomes of much importance to know the general characters of form and 

 mode of development of the cellules. 



In the preceding section it has been shown that the cellules, or the 

 inhabitants of these cellules, are not independent, but all have their origin 

 in a common body which fills the longitudinal canal, and that they remain 

 in constant connection with the same throughout their existence. 



The calycle or cellule is formed by budding from one side of the com- 

 mon body, not unlike many of the Sertularians, except that the cellules 

 are generally close together at their origin.! They are usually more or 

 less oblique to the direction of the axis, as is clearly indicated by the cell- 

 partitions ; and the degree of obliquity often indicates specific distinction. 

 The cellules are for the most part contiguous at their origin, and they 

 sometimes remain in contact throughout their entire length ; but in the 

 greater number of species, there is a small portion of each one free on one 

 side towards the aperture. This character is shown in numerous examples 

 (Plates i, ii and iii). 



In some forms the cellules are contiguous in their lower portions, while 

 the entire upper or outer part becomes free, as seen in G. clintonensis 



* Mr. Caruthers, in his recent paper on Graptolites, assumes that Phyllograptus has 

 no common canal or common body ; but I do not know on what evidence this view is based. 

 There seems to me a narrow semicircular space at the base of each cellule ; and these, 

 communicating longitudinally, form the common canal which is occupied by a continuous 

 body or ccenosarc. 



t The mode of budding and the form and arrangement of the cellules in the Sertula- 

 rians are shown in the accompanying figures of two species of Sertularia (figs. 1 and 2) 

 from our own coast. Fig. 3, with a range of cellules on one side only, is a Plumularia. 



Fig. 1 



[Asseiii. No. 230.] 



Fig. 3. 



t 



Fig. 2. 



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