48 



stages of its development, seems to have been small and feeble, 

 the proximal end of the stipe being somewhat attenuated, and the 

 first cellules stunted in their growth ; but as the stipe increased in 

 length, and successive cellules were budded, it acquired a fuller 

 vitality, and both cellules and common canal attained their full 

 development. 



Neither the young nor the adult Graptolites appear to have been 

 endowed with the power of locomotion. It is true that some of 

 them possessed in the central disc, an organ by which they may 

 have been enabled to float or sink at pleasure, but there is no 

 trace in any of their fossilized remains, of organs by vphich they 

 could move from place to place. If they were really furnished 

 with such organs, they must have been of a membraneous nature, 

 and, like the soft portions of their bodies, would perish and leave 

 no trace behind. It must also be remembered that Graptolites 

 were composite organisms, consisting in some cases of from two to 

 three thousand semi-independent zooids ; and we can scarcely 

 imagine such numerous colonies acting in concert in reference to 

 the direction in which they should travel. The limited knowledge 

 we possess respecting the habits of these interesting creatures, 

 points to the conclusion that although they existed as free organ- 

 isms, yet in all probability they performed the work assigned to 

 them by a beneficent and all-wise Creator, and then died at the 

 place which witnessed their birth. It was otherwise with the 

 members of the Trilobite family living at the same time ; they 

 evidently possessed the power of moving freely from place to 

 place, because solitary specimens may occasionally be met with 

 anywhere in the Skiddaw Slate rocks ; but Graptolites were almost 

 invariably congregated together, so that it may be said of them, 

 as of the Sertularians, that "associated life was the rule, and 

 solitary existence the rare exception." 



Preservation. 



In reference to the preservation of the remains of these organ- 

 isms, it would seem that the stipes have generally been crushed 

 or flattened out, but in some cases the process of fossilization 



