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寡毛双眉虫无性生殖期间的皮膜演化和细胞发生学 总被引:1,自引:0,他引:1
于1991年6月在青岛海区采集到一腹毛目纤毛虫,寡毛双眉虫。应用蛋白银技术研究了其无性生殖期间的细胞发生学,其特征为:1)AZM原基独立地出现于远离模棘毛的前方而非紧靠老的横棘毛附近;2)口棘毛并非来自第一FVT原基(在后仔虫),而是由UM原基分化而来;3)老的AZM将发生后半群的局部重建而非整个地由前仔虫简单继承。 相似文献
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论叠层石的地层学意义 总被引:4,自引:0,他引:4
建议用Burne和Moore(1987)的“微生物岩”一词,以代替广义的“叠层石”:分别取叠层石成因定义与描述定义之长,对叠层石重新给予定义;根据我国学者在叠层石研究中取得的新进展,认为不能简单地用生物控制或环境控制解释其形态成因,并认为在当前单纯依靠叠层石确定前寒武纪地层时代和盆地间地层对比,宜采慎重态度。 相似文献
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E. Hejl D. Coyle Nand Lal P. Van den Haute G. A. Wagner 《International Journal of Earth Sciences》1997,86(1):210-219
Since 1985, apatite fission-track analysis was applied to more than 70 samples from surface outcrops and shallow boreholes
at the western margin of the Bohemian massif. Apatite ages were determined by the grain-population method. Additional information
from the frequency distributions of fully confined spontaneous tracks was used for modelling of t–T paths in the low-temperature
range (<120 °C). Seven zircon samples were dated by the external detector method. Zircon ages between 283 and 215 Ma indicate
unroofing during the Permian molasse stage and the Triassic. Tectonic quiescence and slow subsidence prevailed from the Jurassic
until the middle Cretaceous. In the basement area south of Weiden, a Mesozoic partial annealing zone (for apatite fission
tracks) is now exposed at the surface. Farther north, the basement was affected by stronger Cretaceous and Palaeogene erosion,
which yielded cooling ages between 110 and 49 Ma. This second period of post-Variscan denudation was correlated to reverse
faulting along the Franconian Line.
Received: 30 June 1996 / Accepted: 24 October 1996 相似文献
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中华绒螯蟹幼体消化系统发育的研究 总被引:20,自引:3,他引:20
于1986,1987两年的3-6月,在浙江平湖水产试验场等地采集中华绒螯蟹五期状幼体和一期大眼幼体,对其消化系统发育的研究表明:各期幼体消化道平均全长分别为0.912mm,1.332mm,1.628mm,1.998mm,2.221mm和2.644mm;胃在Z1中呈椭圆形,到Z3方才明显分化成贲门胃和幽门胃两部分;至于贲门胃内的研磨结构和幽门胃内的滤器则要到大眼幼体才完全形成;在各期幼体中,中肠均是消化道最发达的部分肠壁细胞呈圆柱状;肝胰管和中肠前盲囊在Z1中出现,而中肠后盲囊却要到Z2方才形成。 相似文献
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