From stage 12 to birth time(stage 16) the miotics and development of lymphoid cells progressed, the number of small lymphocytes decreased.

• 从胚胎发育12期至出生前(16期)，淋巴细胞不断增殖分化，小淋巴细胞逐渐增多，而淋巴母细胞和中淋巴细胞逐渐减少。