Morphology and sperm membrane reactions: (a) abnormal tail turning, (b) abnormal midpiece upwards, (c) broken neck, (d) abnormal free cell membrane on the head, small head and two tails, (e) no head, (f) pyriform head, (g) tail rotating to the head, (h) coiled principal piece, (i) normal sperm, (j) small round sperm head, (k) abnormal acrosome, (l) distal midpiece reflexes, (m) head free neck, (n) double head, (o) sperm reaction to HOS, indicated by coiled tail, (p) severely coiled midpiece, (q) midpiece interrupted in the middle, (r) tail twisting abnormality at the tip, (s) tail proximal cytoplasmic droplet.