ANCIENT SLATE-INSCRIPTIONS. 57 



were not reproduced after the manner of Sertularians, 

 but were developed by budding. The cups he 

 thinks were filled with protoplasmic matter called 

 Nematophores. From these characters he is induced 

 to place the Graptolites as low down as Rhizopods. 

 We are compelled, therefore, to leave the point in 

 some degree of uncertainty, and to take the tolerably 

 safe position of regarding these curious organisms 

 as being nearly related to Sea-firs, while at the 

 same time they possess some characters of the much 

 lower class of Rhizopoda of which Foraminifera 

 are familiar members. 



These preliminary observations will, it is hoped, 

 enable every reader to understand the following 

 somewhat technical definition of Graptolitoidea 

 given in Nicholson's Manual of Zoology, page 167 : 

 " Hydrosoma (the entire organism) compound, 

 occasionally branched, consisting of numerous poly- 

 pites united by a coenosarc; the latter being enclosed 

 in a strong, tubular, chitinous polypary, whilst the 

 former were protected by hydrothecae (cups). In 

 the great majority of Graptolites the hydrosoma 

 was certainly unattached; but in some aberrant 

 forms doubtfully belonging to the sub-class 

 there is reason to believe that the hydrosoma 

 was fixed. In many cases the hydrosoma was 

 strengthened by a chitiuous rod, the solid axis or 

 virgula, somewhat analogous to the chitinous rod 

 which strengthens the polyzoary in the singular 

 Polyzoon, Rhabdopleura. This axial rod lies in a 

 groove on the dorsal side of the polypary (i.e. on 

 the side opposite to that on which the hydrothecae 



