Cell theory given by Schleiden and Schwann was incomplete because there was no explanation about the foramtion of new cell . This aspect of cell theory was completer by

Options

A. Robert Hooke
B. Virchow
C. Robert Brown
D. Kolliker

Answer

To answer the question regarding the completion of the cell theory initially proposed by Schleiden and Schwann, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Original Cell Theory**:
- The original cell theory, formulated by Schleiden and Schwann, states that all living organisms are composed of cells and that the cell is the basic unit of life. However, it lacked an explanation of how new cells are formed.

2. **Identifying the Gap in the Theory**:
- The gap in the original cell theory was the absence of a mechanism or explanation for the formation of new cells. This was a significant oversight as it did not account for how organisms grow and repair tissues.

3. **Contribution of Rudolf Virchow**:
- Rudolf Virchow, in 1855, contributed to the completion of the cell theory by stating that all cells arise from pre-existing cells. This means that new cells are formed through the division of existing cells, thereby providing a clear mechanism for cell formation.

4. **Revising the Cell Theory**:
- With Virchow’s addition, the revised cell theory can be stated as:
- All living organisms are composed of cells or their products.
- The cell is the basic unit of life.
- All cells arise from pre-existing cells.

5. **Recognition of Other Contributors**:
- While Virchow is credited with completing the theory regarding cell division, it is important to acknowledge that Robert Hooke was the first to discover cells, and other scientists like Robert Brown contributed to our understanding of cell structures.

### Final Answer:
The aspect of cell theory regarding the formation of new cells was completed by Rudolf Virchow, who stated that all cells arise from pre-existing cells.