. Relics of primeval life, beginning of life in the dawn of geological time. Fig. 7<? Portion of ihin section of Cryptozoon proliferum {yi\\\\a^<\ x 50). (a) Corneous layers, (a^) One of these dividing, {b) Intermediate stroma withgranules of calcite, dolomite and quartz, traversed by canals. From a Micro-photograph by PROF. Penhallow. {To face p. 39. LIFE IN THE EARLY CAMBRIAN 39 If now in imagination we cast our tow-net ordredge into the sea of the Lower Cambrian, wemay hope to take specimens illustrative of all oursix groups of invertebrate animals, and underseveral of them example
. Relics of primeval life, beginning of life in the dawn of geological time. Fig. 7<? Portion of ihin section of Cryptozoon proliferum {yi\\\\a^<\ x 50). (a) Corneous layers, (a^) One of these dividing, {b) Intermediate stroma withgranules of calcite, dolomite and quartz, traversed by canals. From a Micro-photograph by PROF. Penhallow. {To face p. 39. LIFE IN THE EARLY CAMBRIAN 39 If now in imagination we cast our tow-net ordredge into the sea of the Lower Cambrian, wemay hope to take specimens illustrative of all oursix groups of invertebrate animals, and underseveral of them examples of more than one subor-dinate group. Of the Crustaceans we might haverepresentatives of four or five ordinal groups, and. Fig, 8.—Diag?-arnmatic section of two Lamina of Cryptozoon, show-ing the Canals of the intermediate space, or Strojna {magnified).Specimen in Peter Redpath Museum. of the Mollusca as many. These are the twohighest and most complicated. In the four lowergroups we would naturally have less variety, thoughit would seem strange, were it not for so manyexamples in later periods, that the dominant andhighest groups should be most developed in regardto the number of their modifications. Of the whole we might perhaps have been ableto secure at least 200 species even in one locality. 40 RELICS OF PRIMEVAL LIFE The likelihood is that if there had been a collect-ing expedition like that of the Challenger in EarlyCambrian times, it could have secured thousandsof specific forms representing all the above types,more especially as we probably know very little ofthe softer and shell-less animals of these old seas,and there is some reason to believe that thesemay have been in greater proportion than
Size: 2381px × 1049px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthordawsonjohnwilliamsir1, bookcentury1800, bookdecade1890
