Hydractinia, Parkeria, and Stromatopora. 73 



the ends of the vertical fibres appear to be most frequently- 

 arranged hexagonally, with one in the centre, thus presenting 

 respectively six horizontal arms, which, together with the 

 ascending and descending one, would make eight. 



We have also to assume, in case of its having been a 

 hexactinellid sponge, the transformation of siliceous into cal- 

 careous material, — not a usual occurrence ; for there are no 

 calcareous sponges with a hexactinellid structure ; indeed they 

 are all fihreless, that is, they consist respectively of a mass of 

 sarcode densely charged with calcareous spicules, like a bag 

 of pins — only, of course, with a definite arrangement. But, as 

 I have just stated, the structure of this species, like that of all 

 the rest of the StromatoporcBj requires to be studied in all its 

 bearings before a correct opinion can be obtained of its original 

 nature. 



Thus, in recapitulation, we have seen the identity that 

 exists between the recent species of Hydractinia and the 

 fossil species of the Sufiblk Crag and Upper Greensand of 

 Haldon Hill, near Exeter, 'respectively ; then the striking 

 resemblance between the chitinous tissue-fibre of the chitinous 

 Hydractiniidse, especially that of Chitina ericopsis^ and the 

 tissue-fibre of Parkeria^ together with that of the radial tubes 

 of the latter to the radiating or vertical tubes of Hydractinia 

 jpliocena ; afterwards the resemblance of Parheria to Loftusia. 

 Then the resemblance of the Lower White Chalk fossil 

 (? Bradya tergestina) to Parheria on the one, and the Stroma- 

 toporcB on the other side ; lastly, the presence in Stromatopora 

 striatella^ of the Upper Silurian System, of a concamerated 

 test in the centre, just as foreign to its structure as the con- 

 camerated test in Parkeria, which Stromatopora otherwise so 

 intimately resembles. 



All this chain of evidence seems to lead to the conclusion 

 that the whole of these organisms, both recent and fossil, 

 were species of Hydrozoa, and neither Foraminifera nor 

 Sponges. 



But foregone conclusions with so-called scientific men, are 

 too often unfortunately like fashion in their governing power, 

 since, although facts may be demonstrated, they are frequently 

 negatived by individuals who, if they reflected, would, from 

 their want of actual experience in this matter, be modest 

 where they are violent in party denunciation. At the same 

 time, as I have long since stated, " in proportion to the gene- 

 ral acquaintance with the lower animals will be the correct- 

 ness of the views respecting them, both recent and fossi- 

 Hzed." 



