The foraminifera: an introduction to the study of the protozoa . er from 018 to 066 mm. Thenucleus often contains more or less numerous smallerbodies (nucleoli). F. E. Schulze described the nucleus of Polystomellastriatopunctata, and stated that it was a round bodyhaving, in some cases, a diameter of 056 mm. andsurrounded by a conspicuous membrane of consider-able thickness; this latter appearance, however, seemsto be exceptional, and Lister remarks that there isusually no perceptible investment of the nucleusother than the reticulum. Highly refracting nucleoli,lying in a clear and apparently
The foraminifera: an introduction to the study of the protozoa . er from 018 to 066 mm. Thenucleus often contains more or less numerous smallerbodies (nucleoli). F. E. Schulze described the nucleus of Polystomellastriatopunctata, and stated that it was a round bodyhaving, in some cases, a diameter of 056 mm. andsurrounded by a conspicuous membrane of consider-able thickness; this latter appearance, however, seemsto be exceptional, and Lister remarks that there isusually no perceptible investment of the nucleusother than the reticulum. Highly refracting nucleoli,lying in a clear and apparently Huid substance, occu-pied the interior. In quite young specimens only one STEUCTUEE AND EEPEODUCTION 23 nucleolus was found, but there were often as manyas twenty or more in full-grown specimens. Schulzealso noticed that the nucleus occupies a position inthe middle third of the series of chambers, and oftenlies partly in one of the narrow canals connecting thechambers, being preserved in its progress from onechamber to another. The position of the nucleus is r. X230 Fig. 14. 1. Nucleus of Polystomella crispa (L.), megalospheric form. 2. Nucleus with larj^evacuolated nucleolus, in P. crispa. 3. Nucleus of same species, which has lostits rounded form, lying within four segments. 4. Nucleus of a megalosphericspecimen of ilotalia Btccarii. After Lister. thus dependent on the number of chambers in theindividual ^ (fig. 16). That the presence of a nucleus is essential for the(jroivth and reproduction of the animal is proved bysuch observations as that of Yerworn, who broke upa specimen of Polj/stoviellu, the larger pieces re-maining alive, as shown by their extended pseudo- For further details of observations on the nucleus of the Foraminiferasee Lister, l]iil. Trans. Boy. Svc. vol. 186b, 1895, pp. 401-453. 24 THE FOEAMINIFEEA podia, and only those fragments that possessed anucleus ^vere able to secrete fresh material to repairthe broken shell. The outer surface of the nucleus,and ev
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