The Annals and magazine of natural history; zoology, botany, and geology . as. Itis certain, however, that they are at present confoimded withthe Polycystina in the well-known fossil gatherings fromOran, Barbadoes, and other places. Of course, where concentric shells are formed at intervals,the mode of growth of the sarcode must be in all essential 226 )r. J. D. Macdonald on the Polycystina. particulars similar to that of the Foraminifera; but where thisnot the case, it is simply continuous or only augmentative.^Though our knowledge of the Polycystina is yet very limited,the two modes of growt
The Annals and magazine of natural history; zoology, botany, and geology . as. Itis certain, however, that they are at present confoimded withthe Polycystina in the well-known fossil gatherings fromOran, Barbadoes, and other places. Of course, where concentric shells are formed at intervals,the mode of growth of the sarcode must be in all essential 226 )r. J. D. Macdonald on the Polycystina. particulars similar to that of the Foraminifera; but where thisnot the case, it is simply continuous or only augmentative.^Though our knowledge of the Polycystina is yet very limited,the two modes of growth here indicated suggest their distri-bution into two corresponding sections, thus :— furuislied with a siliceous spicular or fenestrated framework. \ bimple or continuous . \ r? ^ •; •J ^ j JiKCi/rfiaimn. / JDV concentric accessions { /, •{ • Astromma. Growth ofsarcode Now that the surface pelagic life of the Polycystina is amatter of fact, we can readily account for the occurrence of somany interesting forms in guano. Fiff. 1. Fig. Astromma Yelvertom.
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