. The cell; outlines of general anatomy and physiology. containing one single active nucleus, andthe other containing three, two of which degenerate. It does notmatter whether the two degenerating- nuclei fall to the shareof one or both cells during division, since they behave like yolkcontents. In Desmidiacem we have observed conjugation as it occurs inisolated living cells ; the Zygnernacese teach us its method of pro-cedure in a colony of cells, where several individuals have joinedtogether in rows to form long threads. When, in the thick felt-like masses with which the Algae cover 282 THE
. The cell; outlines of general anatomy and physiology. containing one single active nucleus, andthe other containing three, two of which degenerate. It does notmatter whether the two degenerating- nuclei fall to the shareof one or both cells during division, since they behave like yolkcontents. In Desmidiacem we have observed conjugation as it occurs inisolated living cells ; the Zygnernacese teach us its method of pro-cedure in a colony of cells, where several individuals have joinedtogether in rows to form long threads. When, in the thick felt-like masses with which the Algae cover 282 THE CELL the top of the water, two threads lie in contact with one anotherfor anj considerable portion of their length, conjugation occursbetween neighbouring cells. As a rule all the cells prepare forreproduction at the same time by sending out lateral processes to-wards each other. These fuse at the point of contact, whilst theseparating wall dissolves, and thus transverse canals are formed,which connect the conjugating threads at regular distances, and. Fig. 153.—Spirogyra longata (after Sachs, Fig. 410). To the left, several cells of two fila-ments, which are about to conjugate: they show the spiral chlorophyll bands, in whichcrown-like arrangements of starch grains are lying, as well as small drops of oil. Thenucleus of each cell is surrounded by protoplasm, from which threads stretch to the cell-wall, b, preparatory to conjugation. To the right, A, cells engaged in conjugation: theprotoplasm of the one cell is just passing over into the other at a; in b the two proto-plasmic masses have already united. In B, the young zygotes are surrounded by a wall. resemble the rungs of a ladder (Fig. 153). The protoplasmicbodies of the cells then contract away from their cellulose wall,and after a time fuse together. Differences which in themselves are trifling, but which on that THE VITAL PROPERTIES OF THE CELL 283 very account are interesting, are seen in various species ofZtjgyiemace
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