. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. [.S6 N. M. STEVEN- SPERMATOGONIA. As in nihrr vertebrates tin- tc>u-s om>Ut of much coiled t.ulmle- in hich, in mature animal-. -Merman >.u«nua and Sertoli- cfll- a IT found at the- periphery against the wall of the tulmle: then coiiK1 lirsi and sccoiul sprrniati H- it--^ in -ari stages, -l>rrmatid>, and unri|)L- s])crmatozoa attached to long processes ru-ndiiv^ from tin- Sertoli-cells toward tin- criitcr of tlic tulmle, -|)i-niiato/().i licin- found in or near the lumen of the tubule.. I-'H.. i . u. l.'