. The Cambridge natural history. Zoology. Ill foraminifp:ra 6g only exogamously} The fusion of their nuclei takes place after some delay: ultimately the zygote nucleus divides into two, a shell is formed, and we have the microsphere, which is thus pluri-nucleate ab initio. As we have seen, the nuclei of the microsphere are ultimately replaced by chromidia, and the whole plasmic body divides into pseudopodiospores, which grow into the megalospheric form. In the Perforate genera, Fatellina and Discorbina, plastogamy precedes brood formation, the cytoplasms of the 2-5 pairing individuals contract
. The Cambridge natural history. Zoology. Ill foraminifp:ra 6g only exogamously} The fusion of their nuclei takes place after some delay: ultimately the zygote nucleus divides into two, a shell is formed, and we have the microsphere, which is thus pluri-nucleate ab initio. As we have seen, the nuclei of the microsphere are ultimately replaced by chromidia, and the whole plasmic body divides into pseudopodiospores, which grow into the megalospheric form. In the Perforate genera, Fatellina and Discorbina, plastogamy precedes brood formation, the cytoplasms of the 2-5 pairing individuals contracting a close union; and then the nuclei proceed to break up without fusion, while the cytoplasm. Fig. 17.—Shell of Globigerina bidloides, from tow-net, showing investment of spines. (From Wyville Thomson.) aggregates around the young nuclei to form ainoebulae, which acquire a shell and separate. In both cases it is the forms with a single nucleus, corresponding to megalospheric forms that so pair, and the brood-formation is, mutatis mutandis, the same as in these forms. Similar individuals may reproduce in the same way, in both genera, without this plastogamic pairing, which is therefore, though probably advantageous, not essential. If pseudopodiospores form their shells while near one another, they may coalesce to form monsters, as often happens in Orhitolites} The direct economic uses of the Foraminifera are perhaps greater than those of any other group of Protozoa. The Chalk is 1 "Which probably accounts for the earlier failure of Lister and of Sohaudinn himself to note their conjugation. 2 Rhumbler, " Die Doppelschalen v. OrbitolUesu. and. Foraminiferen," mArch. Protist. i. 1902, p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipl
Size: 2288px × 1092px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
