File:Quarterly journal of microscopical science (1891) (14803495953).jpg

Identifier: quarterlyjournal339192lond (find matches)
Title: Quarterly journal of microscopical science
Year: 1853 (1850s)
Authors:
Subjects:
Publisher: London, J. and A. Churchill (etc.)
Contributing Library: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library
Digitizing Sponsor: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library

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enerativenucleus undergoes two mitoses and so forms four gametonuclei. SOME PEOBLEMS OF EEPEODUCTION. 37 nucleus occur as follows :—The first differentiates an Apical(N^a) and a Basal nucleus (N^b) respectively. Each of theseagain divides to form a pair of nuclei nearly superposed, whichwe term and letter Apical (N^a), Subapical (N^sa), Subbasal(N%b), and Basal (N^b) respectively. Each of these fouragain divides to form a pair of nuclei of the degree N^. TheApical pair (N^a + N^a) and Basal pair (N^b + N^b) are col-lateral; the Subapical and Subbasal pairs are superposed toform a file of four nuclei, which we name and letter Upperand Lower Subapical (N^usa + N^lsa), and Upper and LowerSubbasal (N^usb + N^lsb) respectively. Of the cytoplasmlining the cell-wall and surrounding the immense centralvacuole, each nucleus attracts a certain portion so as to forma naked free celP somewhat ill-defined, and indeed any-thing but free. The following schema (Fig. 4) shows the for- Egg apparatus.
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Endosperm fZ nucleus. Antipodalcells. Fig. 4.—Schema of divisions in embryo-sac; the vertical lines separatesuccessive stages. 38 MAECUS M. HAETOG. mation of these cells and their position in the mature embryo-sac ready for fertilisation ; the dotted vertical lines indicatesuccessive stages. The symmetrical relation of the eightcells formed is in no way exaggerated in the figure. Of the eight cells so formed not one is capable of ulteriorindependent development; though it appears from Stras-biirgers figures/ and those of other authors, that enoughinterval is left between the mitoses for the nuclei each timeto resume a resting state. Hence it cannot be the extremerapidity of the mitoses that determines the reproductive in-capacity of these cells. The fate of these eight cells is verydifferent. (1) The Apical Pair or Synergids^ aptly termed Gehiil-finnen (handmaids) by Strasbiirger, are utilised as the channelfor the transmission of the male pronucleus, sometimesundergoing a complete

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