二种环节动物皆具有闭锁循环系，包括管状的心脏及背血管，腹血管。用大头针标示二标本的下列构造：。
Both annelids possess a closed circulatory system with tubular hearts and a dorsal and ventral blood vessel. In both specimens, pin the following.
二种环节动物皆具有闭锁循环系，包括管状的心脏及背血管，腹血管。用大头针标示二标本的下列构造：。
Both annelids possess a closed circulatory system with tubular hearts and a dorsal and ventral blood vessel. In both specimens, pin the following.
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