HARDWICKE'S SCIENCE- GOSSIP. 



1S1 



ther, so that they are all in contact (fig. 121), where- 

 as in the modern Sertularians they are distinct. In 

 one genus of Graptolites, however, the cups are 

 separate, and from the resemblance they have to the 

 teeth of a rake (L. raster, "a rake"), 

 these forms go by the name of Rastrites 

 (fig. 123). The latter are usually 

 coiled up like toothed watch-springs, 

 and they are among the prettiest of all 

 the Graptolites. Their resemblance 

 to the brass-toothed wheels of watches 

 is often still further borne out by the 

 cieso'f ditto, Rastrites having had their substance 

 magnified. converted into iron pyrites, the gilt 

 outlines standing forth in very bright 

 relief from the surfaces of the black shales in 

 which they are imbedded. 



Fig. 121. Caly- 



Fig. 122. Double Graptolite {Diptugraptus prist is). 



These toothed projections, seen on the outer 

 margins of both single and double Graptolites alike, 

 are regarded by most naturalists as identical with 

 the cups of recent " Sea- firs," or Sertularians, and 

 therefore as having contained zoophytes when the 

 Graptolites were alive. Professor Allman, how- 

 ever, doubts whether the Graptolites had any cups 

 at all, and thinks that these projections were like 

 those to be seen on the embryonic stem of the 

 lobster's horn coralline {Antennularia), which bear 

 nematophores. Dr. Nicholson figures the egg- 

 bearing capsules of Graptolites in his "Manual of 

 Palaeontology," and his " Monograph of the Grapto- 

 lidce" where he sets forth their resemblance to the 

 gonothec(B of the Sertularians. He states that he 

 found them both attached to the branches of the 

 Graptolites, and separate, and has no doubt as to 



their being the egg-bearing cases of the ancient 

 Graptolites. Neither Allman nor Carruthers, how- 

 ever, assents to this conclusion. The former be- 

 lieves that the Graptolites did not bear egg-cases at 

 all, but developed themselves by budding, just as 

 the banks 'of that oceanic sea-weed called Saryas- 

 sum are formed. In the possession of the cups, 

 perhaps filled with protoplasmic matter, called 

 nematophores, Professor Allman thinks the Grapto- 

 lites were nearly related to rhizopod animals, and 

 thus included characters now belonging to two well- 

 marked groups of marine animals. 



Fig. 123. Group of Graptolites ; b, pastrites. 



All naturalists are agreed that the Graptolites 

 differed from the " Sea-firs " in not being rooted, as 

 the latter always are. They were therefore free, 

 and no doubt gathered in great banks, 

 as would appear from the usual way 

 in which they are found fossilized. 

 So far, their development by budding, 

 after the manner of the Sargassum, or 

 " Gulf-weed," would appear to be 

 probable. Mr. John Hopkinson has 

 shown that Graptolites are capable 

 of being grouped into two great divi- 

 sions, in one of which a fibrous rod 

 strengthened the outside of the single 

 Graptolites, or was in the centre in 

 the doubled species. This rod, Nichol- 

 son thinks, was originally hollow, and 

 filled in with living material. It must 

 not be confounded, however, with the 

 hollow space {ccenosarc) communicat- 

 ing with each cup, which was un- 

 doubtedly filled with the "common 

 flesh." The Graptolites, which 

 possessed these rods are called Rhab- 

 dop/tores: all of them were free and Fig. 124. single 



, i t> i. ii ■ *i Graptolite 



unrooted. But there is another group (Graptuiuhus 

 of Graptolites of more complex struc- P™d<m). 

 ture, often branched and " dendroid," 

 or " tree-shaped," like the Sertularians. These 

 are termed Cladophora, and Mr. Hopkinson has 



