Which of the following is not a character of phylum hemichordata?

Options

A. Presence of notochord which is mesodermal in origin
B. Excretory organ is proboscis gland
C. Circulatory system is open
D. Respiration takes place through gills

Explanation

To determine which of the following is not a character of phylum Hemichordata, we will analyze the characteristics of this phylum and compare them with the options provided.

### Step-by-Step Solution:

1. **Understand Hemichordata**: Hemichordata is a phylum that serves as a connecting link between chordates and non-chordates. Members of this phylum exhibit some characteristics of both groups.

2. **Identify Key Characteristics of Hemichordata**:
- Presence of a dorsal hollow nerve cord (similar to chordates).
- Excretory organ is the proboscis gland.
- Circulatory system is of the open type.
- Respiration occurs through gills (pharyngeal gills).

3. **Analyze the Options**:
- **Option 1**: Presence of notochord which is mesodermal in origin. (This is a characteristic of chordates, not hemichordates.)
- **Option 2**: Excretory organ is the proboscis gland. (This is true for hemichordates.)
- **Option 3**: Circulatory system is of open type. (This is true for hemichordates.)
- **Option 4**: Respiration takes place through gills. (This is true for hemichordates.)

4. **Conclusion**: Since the presence of a notochord is a characteristic of chordates and not hemichordates, **Option 1** is the correct answer as it does not belong to the characteristics of phylum Hemichordata.

### Final Answer:
**Option 1: Presence of notochord which is mesodermal in origin.**

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