image<\/p>\n\n\n\n
Figure 3\u20135. Fertilization and division of cells in parasitic worms \r\nAscaris (After van Beneden, 1883; From A. Mirsky. In: Molecules \r\nand Cells, vol. 4, 1969). \r\n1 \u2014 approach of the nuclei of spermatozoon and ovum; 2, 3, 4 \u2014 the \r\nnuclear envelope is break down and the chromosomes are clearly \r\ndiscernable; in every nucleus there are two chromosomes \u2014 a half of \r\nthe normal diploid chromosomal set; 5, 6 \u2014 preliminarily, each \r\nchromosome is divided in two; 7 \u2014 the divided chromosomes separate; \r\n8, 9, 10, 11 \u2014 two centrioles appear, a dividsion spindle is formed \r\nbetween them; cell division begins; 12 \u2014 two cells are formed, there are \r\nfour chromosomes in each nuclei. Two of them originate from the ovum, \r\nthe other two \u2014 from the spermatozoon. <\/pre>\n\n\n\nThe nucleus or the Nuclear Equivalent (Nucleid) – Obligatory and Irreplaceable Organelle of Each Cell<\/h2>\n\n\n\n
Section 3.3.<\/strong> The discovery of cell nucleus is an important stage in understanding its
biological essence and development. According to literary data (see
Katznelson, 1939, 1963; History of Biology, 1972, 1975) the first who has
observed a nucleus in fish erythrocytes is Antony van Leeuwenhoek, but
his observations have not come to light. Fontana (1781) has depicted
nuclei in epithelial cells of snake epidermis. Then nuclei are observed by F.
Cavolini, J. Purkinje, Ch. Mirbel, F. Meyen, J. M\u00fcller, etc., but they have not
estimated their role and importance. At that time even the term \u201ccell\u201d have
not possessed a definite interpretation. Different terms have been used \u2014
\u201cgrains\u201d, \u201cballs\u201d, \u201cpouchs\u201d, etc. Recognizing the nucleus as a constituent of
plant cells is a merit of the English botanist Robert Brown (1833), who has<\/p>\n","protected":false},"excerpt":{"rendered":"image Figure 3\u20135. Fertilization and division of cells in parasitic worms Ascaris (After van Beneden, 1883; From A. Mirsky. In: Molecules and Cells, vol. 4, 1969). 1 \u2014 approach of the nuclei of spermatozoon and ovum; 2, 3, 4 \u2014 the nuclear envelope is break down and the chromosomes are clearly discernable; in every nucleus […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[6],"tags":[],"class_list":["post-749","post","type-post","status-publish","format-standard","hentry","category-book"],"_links":{"self":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/749","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=749"}],"version-history":[{"count":1,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/749\/revisions"}],"predecessor-version":[{"id":781,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=\/wp\/v2\/posts\/749\/revisions\/781"}],"wp:attachment":[{"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=749"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=749"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cellandcelldivision.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=749"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}