Which of the following statements is incorrect regarding organisms of phylum Chordata?

Options

A. The organism are characterized by the presence of a notochord and a ventral hollow nerve cord
B. They are triploblastic and bilaterally symmetrical
C. They have a ventral heart
D. They are further divided into three subphyla.

Answer

To solve the question regarding which statement is incorrect about organisms of phylum Chordata, we can analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Phylum Chordata**:
- Organisms in this phylum are characterized by the presence of a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some stage of their life cycle.

2. **Analyzing Each Statement**:
- **Option 1**: "Organisms are characterized by the presence of notochord and a ventral hollow nerve cord."
- This statement is incorrect because chordates possess a **dorsal** hollow nerve cord, not a ventral one.

- **Option 2**: "They are triploblastic and bilaterally symmetrical."
- This statement is correct. Chordates are indeed triploblastic (having three germ layers: ectoderm, mesoderm, and endoderm) and bilaterally symmetrical.

- **Option 3**: "They have a ventral heart."
- This statement is also correct. Chordates, particularly vertebrates, typically have a ventral heart.

- **Option 4**: "They are divided into three subphyla."
- This statement is correct. Chordates are divided into three subphyla: Urochordata, Cephalochordata, and Vertebrata.

3. **Conclusion**:
- The incorrect statement regarding organisms of phylum Chordata is **Option 1**.

### Final Answer:
The incorrect statement regarding organisms of phylum Chordata is **Option 1**: "Organisms are characterized by the presence of notochord and a ventral hollow nerve cord."