Figure 3. Stages of the seminiferous epithelial cycle of the rabbit, modified from Swierstra and Foote (1963). Transcripts for protamine-1 and protamine-2 are present in the cytoplasm from step 5 round spermatids (stage I) to step 11 elongated spermatids (stage VII). No in situ hybridization signals can be observed in stage VIII of the cycle.