File:The American Museum journal (c1900-(1918)) (18160690871).jpg

Title: The American Museum journal
Identifier: americanmuseumjo06amer (find matches)
Year: c1900-(1918) (c190s)
Authors: American Museum of Natural History
Subjects: Natural history
Publisher: New York : American Museum of Natural History
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: Biodiversity Heritage Library

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
THE DEVELOPMENT OF A MOLLUSK 35 particular significance in the preparation of the eggs for fertiHza- tion. The process is known as the "maturation" of the egg. The sperm cells are inclosed with the ova in the capsules. They consist chiefly of a nucleus with a very insignificant amount of protoplasmic substance. A single sperm cell enters the ovum somewhere about the vegetative pole, at the time of the beginning of the maturation process, and its nucleus gradually makes its way upward toward the Q<g% nucleus, until the two nuclei are in contact. These nuclei, known as the "pronuclei" of the egg, may be seen in Model i,B lying close together in the protoplasm at the animal pole. The egg is now fertilized and capable of developing into a new organism.
Text Appearing After Image:
MODEL 1, B The fertilized egg, showing the Qg^ and sperm nuclei in contact at the animal pole. On either side of them are the centrospheres. Each nucleus is composed largely of a peculiar substance, which has been given the name "chromatin," because of the readiness with which it assumes the stains used for coloring microscopic objects. Though little is known about the definite function and properties of chromatin, its importance is evidently very great, for it is found in the nuclei of all cells. Generally it is

Note About Images