Translation of "‎개중에는" in English

‎개중에는 힘이 쭉 빠지는 ‎연체동물도 있습니다 ‎껍데기의 꼭대기에 ‎정확히 구멍을 뚫으면 되죠 ‎벌림근에요

But some of these mollusks will only relax if that drill is precisely in the apex of the shell, on the abductor muscle.