The following are some statements about leucocytes. Which of these is incorrect?
I. The most abundant leucocyte is a granulocyte, whereas the least abundant leucocyte is an agranulocyte.
II. The largent leucocyte is a granulocyte, whereas the smallest leucocyte is an agranulocyte.
III. Phagocytic leucocytes may be agranulocyte or granulocyte.
IV. Polymorphonuclear leucocytes are the largest granuocyte, whereas the largest agranulocyte has a kidney-shaped nucleus.

Options

A. I, II and III
B. II and IV
C. III and IV
D. I and II

Answer

To determine which statements about leucocytes (white blood cells) are incorrect, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement I**: "The most abundant leucocyte is a granulocyte, whereas the least abundant leucocyte is an agranulocyte."
- **Analysis**: The most abundant leucocytes are indeed granulocytes, specifically neutrophils. However, the least abundant leucocytes are basophils, which are also granulocytes, not agranulocytes. Therefore, this statement is incorrect.

2. **Statement II**: "The largest leucocyte is a granulocyte, whereas the smallest leucocyte is an agranulocyte."
- **Analysis**: The largest leucocyte is a monocyte, which is an agranulocyte, not a granulocyte. The smallest leucocytes are lymphocytes, which are also agranulocytes. Therefore, this statement is also incorrect.

3. **Statement III**: "Phagocytic leucocytes may be agranulocyte or granulocyte."
- **Analysis**: This statement is correct. Both neutrophils (granulocytes) and monocytes (agranulocytes) are phagocytic, meaning they can engulf and digest foreign particles.

4. **Statement IV**: "Polymorphonuclear leucocytes are the largest granulocyte, whereas the largest agranulocyte has a kidney-shaped nucleus."
- **Analysis**: Polymorphonuclear leucocytes (PMNs) refer to neutrophils, which are indeed the most abundant granulocytes, but they are not the largest. The largest agranulocyte, monocyte, does have a kidney-shaped nucleus. Therefore, this statement is partially correct but misleading regarding the size of PMNs.

### Conclusion:
- The incorrect statements are **I** and **II**.

### Final Answer:
The incorrect statements about leucocytes are **I and II**.