Fertilization is external, producing free-living planula larva.

体外，能产生自由活动的浮浪幼虫。

Traditionally, doctors use gestational age, the number of weeks from fertilization to birth, to determine whether a preemie should receive invasive care.

传统上，医生们用孕龄，到出生的周数来决定极早产儿是否接步的关注。

4 Turbellarians are monoecious with the reproductive systems adapted for internal fertilization. And the monogenetic flukes (class Monogenea) are mostly ectoparasites of fishes.

涡虫是雌雄同体的，生殖系统适于体内。单起源的吸虫（单殖纲）大多是鱼的外寄生虫。

A long-term field experiment was carried out to study the effect of fertilization on the organo-mineral complexation and the combined forms of humus of phaeozem in Jilin Province, China.

摘要利用长期定位试验研究了施对黑土有机无机复合及腐殖质结合形态的影响。