HISTORY OF RESEARril. xix 



litic rescnrcli, niid in tlie sul)j(>ct^5 treated of in the sul)se(|ueiit sections of liis nienioir, 

 Intel' ()l)servei's liave made eoiisideial)le advances upon liis (tiM^inal \ie\vs. 



8. iMoih'. of (Iro/flh oj'tlLc (ir((i)luliles.^\\\\vv\\m\v^ viewoF the method of ^Towth 

 of the (Jraptolites is very different from that accejtted at tlie pi'esent (hi v. 

 Observing that the polyparj increased in width in one (the distal) direction and 

 decreased in the other (the proximal), he considered that the proximal part 

 with the smaller cells was the younger, or, as he termed it, the (/roiriiK/ pDrHoii, 

 while the widest part (distal) was the adult porHoii. He concluded that " the 

 growth of the polypary took place, therefore, by the successive appearance of new 

 'germs' at the narrow end." These germs are at first very distant (as in (Ir. 

 protciis), while in the adult portion they are in contact. He Avas therefore of the 

 opinion that the "elongation of the body of the polypary must have preceded the 

 production of any new germ. Thus this body would seem to have served as a canal 

 of propagation." Barrande, however, points out that there are at least two foreign 

 species in which such a mode of growth is impossible, viz. Gr. Miirchisoni and 

 Gr. gemiiiits. These consist of two branches united by a small terminal " stem." 

 In these forms lie seems clearly to have realised that the growth must be in the 

 opposite direction to that advocated by himself for the Bohemian forms. 



Again, the fact that many single- and double-celled forms show a naked axis 

 prolonged l)eyond the so-called adult end, Bari'ande considers may be explained by 

 the " perishing of the older cells, one after the other, as the younger cells are 

 developed." The occasional prolongation of the axis also beyond the narrow end 

 of the polypary can, according to Barrande, only be interpreted by the " accidental 

 decomposition of the young cells after the death of the individual before fossilisa- 

 tion." Another difficulty, presented by the not infrequent decrease of the cells 

 towards the adult end, is also explained by him in the same way. Considering the 

 cautious deductions from facts observed in most of the other parts of this book, it 

 might appear strange at first sight that Barrande should have adopted so definitely 

 this theory as to the method of growth; but it must be remembered that at that 

 time the complex Canadian forms, in which such a mode of growth is demonstrably 

 impossible, had not l)een desci'ibed. 



9. Mode of Existence. — As respects the mode of existence of the Graptolites, 

 Barrande only considers the single question whether the Graptolites Avere free or 

 fixed ; and he agrees with M'Coy that, as far as the evidence of the Bohemian 

 species goes, it is " very probable that they were entirely independent." There is 

 no evidence of adherence of Graptolites to rocks, as is the case with modern 

 Zoophytes and Molluscs. It would have been impossible for them to be fixed to 

 the ground by the growing portion, on account of its slender and frequently curved 

 character, and there is no evidence wdiatsoever to suggest that they Avere fixed by 

 the adult end. With regard to such forms as Gr. hicornis and Gr. Mnrchisoni, 

 hoAVCA'cr, Barrande considers that the invariahle presence of a "point" or 



