10 



MORPHOLOGV OF THE CELL. 



cell conjugates with two others, and takes up both their protoplasm-masses ; in these 

 cases the zygospore is the product of three cells. In the Myxomycetes the swarm-cells 

 (Myxo-amceba:), which are endowed with a peculiar motion, coalesce gradually in great 

 numbers, and finally form large, motile, naked protoplasm-masses, the Plasmodia, which 

 only at a subsequent period are transformed into a number of cells. 



In the cases hitherto considered the uniting protoplasm-masses are of equal size ; 

 the process of fertilisation in many Cryptogaijis differs from them only in the fact 

 that the two protoplasm-masses which coalesce .are of unequal size, and otherwise 

 of different properties. In Book II. we shall treat in detail of the reproduction of 

 Cryptogams; here we need only state that the male fertilising bodies (antherozoids) 

 of Cryptogams are usually motile naked protoplasm-masses, that is, primordial cells ; the 

 female organ of these plants usually opens outwardly, and contains a primordial cell 



<iw^ 



VlG. 6.— Spirogyra longata. A cells in the act of conjugation; at 

 a the protoplasm of one cell is passing over into the other; at b this has 

 already taken place ; the chlorophyll-band is still partially recognisable. 

 B the young zygospores surrounded by a cell-wall; the protoplasm con- 

 tains numerous drops of oil ( X 550). 



Fig. 5. — Spirogyra longata. Cells of two filaments in an early stage of conjugation, showing the spirally coiled chlorophyll-bands, 

 in the chlorophyll-granules of which lie rings of starch-grains ; small drops of oil are also distributed through them (see Sect. 6) This 

 is the condition of the chlorophyll after the action of strong sunlight ; the nuclei are also to be seen in the cells, each surrounded by 

 protoplasm, threads of which reach the cell-wall in different places ; a and b are the pjotuberances in two different stages (X 550). 



(oosphere) which is fertilised by the antherozoids. In cases which have been accurately- 

 observed ((Edogonium, Vaucheria) these coalesce with the former, and the new cell 

 results from this coalescence. As with the Conjugatae and some Fungi, the cell formed 

 in this manner is always a reproductive cell; with it begins the growth of a new 

 individual plant. 



3. Free Cell-formation. — In the protoplasm of a cell new centres of formation 

 arise, round each of which a portion of the protoplasm collects, and forms a cell. 

 A portion of the protoplasm may remain and represent the protoplasm-mass of 

 the mother-cell which persists for a longer or shorter time. [The new centres of 

 formition are indicated by the previous appearance of nuclei formed by the repeated 



