14 



FUNDAMENTALS OF CYTOLOGY 



2. The nuclear multiplication may be accompanied regularly by the 

 development of partition membranes, the result here being the multi- 

 cellular mass so familiar in the tissues of most animals and plants. 



3. As the nuclei multiply, the cytoplasm may not subdivide com- 

 pletely but gradually forms a network, commonly with its larger portions 

 containing the nuclei and remaining continuous with one another through 

 narrower strands. Such a pattern is found in some animal connective 



Multinucleate Man 



Multicellular Mass 



3 



Network 



Cell Cluster 



Cells in Matrix 



Free Cells 



Fig. 5. — Diagram illustrating development of six different protoplasmic growth patterns 

 from a typical protoplast. Explanation in text. 



tissues (Fig. 6). The network lies embedded in a substance that may 

 contain cells of additional types. 



4. Each nuclear division may be followed by a cytoplasmic division, 

 the resulting cells rounding up from one another but remaining in contact 

 as a cell cluster. This pattern characterizes a certain stage (morula) of 

 certain animal embryos (Fig. 94), and it is also seen in "colonial" algae 



(Fig. 7). 



5. After nuclear and cell division the individual cells may become 

 separated by the accumulation of an intercellular substance (matrix) 

 secreted by the protoplasm during their formation and growth. The 



