Define deuterostomous condition.

Explanation

### Step-by-Step Solution:

1. **Definition of Deuterostomous Condition**:
The deuterostomous condition refers to a developmental process in certain animals where the first opening that forms during embryonic development becomes the anus, while the mouth develops later.

2. **Formation of Blastula**:
The process begins after cleavage, where a hollow structure called the blastula is formed. This occurs at the 15 to 30 cell stage of development.

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