The foraminifera: an introduction to the study of the protozoa . cytoplasts Plastogamy. Hartog definesPlastogamy as the cytoplastic union of cells without 1 Ueber Hastoganiie bei Foraiu., Sit^:. Gesellsch. , 1895, No. 10. STEUCTURE AND EEPRODUCTION 31 nuclear fusion. The plastogamic reproduction ofDiscorhina is shown by Schaudinn to occur asfollows. The Hat or inferior faces of the tests arebrought together with the apertures coinciding. Thew^alls of the last formed chambers are sometimesresorbed, and an enclosing shell made around thespace between the tests. Then follows
The foraminifera: an introduction to the study of the protozoa . cytoplasts Plastogamy. Hartog definesPlastogamy as the cytoplastic union of cells without 1 Ueber Hastoganiie bei Foraiu., Sit^:. Gesellsch. , 1895, No. 10. STEUCTURE AND EEPRODUCTION 31 nuclear fusion. The plastogamic reproduction ofDiscorhina is shown by Schaudinn to occur asfollows. The Hat or inferior faces of the tests arebrought together with the apertures coinciding. Thew^alls of the last formed chambers are sometimesresorbed, and an enclosing shell made around thespace between the tests. Then follows the breakingup of the nuclei, and the formation of embryonicyoung, which speedily form their own investmentto the extent of two or three chambers beforebreaking away from the enclosing shell. 32 THE FOEAMINIFERA CHAPTER IV THE SHELL STRUCTURE OF THE FORAMINIFEEA ANDTHEIR PLANS OF GROWTH It is due to the fact that the Foraminifera presentsuch an extensive variety of regular and beautifulforms that their shells are so much in favour withbeginners in Fig. 18. a, Test of Cristellaria crepidula (F. and M.); h, siliceous internal cast of thesame species from flint-meal, Upper Chalk. Highly .magnified. After Eleij. The plan of the shell is dependent upon thearrangement of the continuously budded segments,and this is partially determined by the form ofthe primordial or initial chamber. It may be that ofa straight series of segments, gradually increasing THE SHELL STRUCTUEE 33 ill size, as in Nodosaria ; curved, as in Mavginulina ;or coiled, as in Botalia. The shell is, as it were, moulded upon thesarcode of the organism, and when we can obtaina cast of the shell—and this often happens in thecase of the fossil Foraminifera—we have a perfectrepresentation of the form of the animal (, 19). This feature of continuous segmentation of the
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