366 Prof. Allman on the Morpliology 



were flexible, and that the solid parts, which are all that have 

 come down to us, were of a hornj or chitinous consistence. 

 There is also evidence to show that, though some obscure 

 forms [DendrograjJtus) ^ associated on insufficient grounds with 

 the graptolites, were apparently rooted, the true graptolites 

 were never directly attached to any other bodies — thus differ- 

 ing from the hydi'oid trophosomes and most of the corals and 

 Polyzoa of the present day. 



We are absolutely ignorant of the original contents of the 

 main tube and of its lateral offsets, and we know just as little 

 of other soft parts which may have accompanied the chitinous 

 skeleton ; so that in attempting to assign to the graptolites 

 their position in the system of nature we are driven to analogy, 

 by no means close, as our sole guide. 



The resemblance of the forms just described to the tropho- 

 some of a calyptoblastic hydroid (sertularian or plumularian) , 

 after the disappearance of all the soft parts, is sufficiently 

 obvious. And it is this resemblance between the fossil grap- 

 tolite and the recent chitinous skeletons of the sertularian and 

 plumularian hydroids which has induced modern palseontologists 

 to refer the fossil to the order Hydroida, regarding the lateral 

 offsets as hydrothecse and the main tube as the chitinous 

 perisarc of the hydrocaulus*. 



We shall presently consider whether the exact points of 

 contact between the graptolites and hydroids have been indi- 

 cated in this comparison. 



The fact which most obviously opposes itself to an accept- 



* The sertularian affinities of the graptolites have been strongly insisted 

 on by Hall, who has greatly advanced our knowledge of these fossils in 

 his classical work, ' Graptolites of the Quebec Group,' which forms one of 

 the memoirs of the Geological Survey of Canada. On the structure and 

 principal modifications of graptolites, the works of Barrande (' Graptolites 

 de Boheme ') and of Geinitz (' Versteinerungen der Grauwacken. Die 

 Graptolithen ') should also be consulted. The sertularian affinities of 

 graptolites have also been defended by Mr. W. Carruthers, of the Botanical 

 Department, British Museum ; and I know of no one who has worked out 

 this question with so much care and completeness : see especially his 

 '' Revision of the British Graptolites " in the ' Geological Magazine,' vol. v. 

 The hydroid relations of the graptolites are also maintained from the same 

 point of -view by Dr. Nicholson in various publications, in which he has 

 largely contributed to our knowledge of these bodies, and more especially 

 in his ' Monograph of the British Graptolitidse,' part 1, just published. 



I must here express my thanks to Mr. Carruthers for the liberal way in 

 which he has placed at my disposal his large collection of gTaptolites, and 

 for the aid which I have derived from his extensive acquaintance with 

 the literature of the subject ; and to Mr. Woodward, of the Palaeonto- 

 logical Department, British Museum, for the readiness vsdth which he 

 jjlaced in my hands for examination the fine collection of graptolites in 

 the Museum. 



