The anterior part of the testis acts in spermatogenesis maintenance and displays high regenerating potency. (a), 11 months after its separation from the anterior part linked to the lung (Lu), the first testis lobe is reduced to glandular tissue (GT) and there is no more spermatogenesis whereas the control testis of the same male has incorporated new germ cells in a zone with early spermatogenic stages (ZES). (b), histological section of the glandular tissue (GT) of the operated testis shown in a: germ cells (GC) with a polylobular nucleus are present in the vicinity of the efferent ducts (ED). (c), A regenerated testis lobe (RTL) near the lung (Lu) observed 8 months after the ablation of the differentiated testis lobe of a 16-month-old male. (d), Histological section of the regenerated testis lobe showing lobules (Lo) containing numerous germ cells at the beginning of spermatogenesis (Sp). (e), Histological section of the most anterior part of a regenerated testis lobe (APT) showing many primordial germ cells in the vicinity of the lung (Lu).