XVI INTRODUCTION. 



they appear to consist of serpentine. The crystalloids of 

 1 ' white pyroxene " are strongly affected with cleavage, which is 

 more or less represented by open gashes the openness of which 

 is disclosed by an infilling of calcite : it frequently happens 

 that the cleavage is imperfectly developed, especially when the 

 mineral is in a translucent condition ; which is occasionally the 

 case. The crystalloids when much gashed are reduced to plates 

 more or less separated ; and in many instances the plates are 

 converted into fibres, somewhat mimetic of those characteristic 

 of the " proper wall " (see woodcut, p. Ivii). No cases have 

 occurred to us of typical " canal system." In numerous cases 

 the reduction of the crystalloids has resulted in the complete 

 removal of their substance, and its replacement by calcite. 



Although our specimen of " Eozoon mineralized with loga- 

 nite" differs from those which S. Hunt had under his observa- 

 tion, we can quite conceive the existence of specimens of the 

 latter kind, inasmuch as the crystalloids through solvent action 

 may have disappeared altogether, and been replaced by " ferri- 

 ferous dolomite." 



The specimen closely corresponds with a rock occurring in 

 Connemara, made up of layers of serpentine and malacolite, and 

 which we have elsewhere (p. 2) called malacolophyte : the 

 resemblance is so close that the crystalloids of malacolite in the 

 latter are widely gashed with corroded cleavage, and the gashes 

 similarly filled with calcite. This peculiarity is so much de- 

 veloped that when it first came under our notice we were imme- 

 diately struck with the idea that the calcite had originated 

 from chemical changes in the malacolite. It is now fifteen 

 years since we formed this opinion ; and it has been completely 

 established by our observations on malacolite or a closely allied 

 mineral from Ceylon, Aker (Finland), Isle of Skye, New Jersey, 

 Porthlisky (Pembrokeshire), and Mont St. Philippe (Vosges). 

 We take the specimen of " Eozoon mineralized with loganite " 

 as another evidence in our favour. 



We now beg to call Dr. Hunt's attention to one other point in 



