Caption as it appears now:

Figure 4. Examples of altered brain scaling relationships.
Solid and dashed lines in (A–C) indicate hypothetical standardized major axis (SMA) scaling relationships of brain region volume (y variable) with brain size (x variable). (A) Altered slopes (β1 and β2), which preclude further scaling analyses using these methods. (A). Groups share a common scaling slope and y-intercept (y1) but average brain size differs between groups (×1 and ×2), producing an x-axis shift. (C) Groups share a common scaling slope and average brain size (×1) but y-intercepts (y1 and y2) are shifted, producing a grade shift. (D) Solid and dashed lines represent actual SMA scaling regressions of mushroom body volume versus remainder-of-central-brain volume (ROCBV) for mature P. pilifera minors (circles) and mature P. pilifera majors (squares), representative of a grade shift accompanying a shift along the x-axis. Dashed line in (d) indicates slope of 1 (isometry) for reference.
doi:10.1371/journal.pone.0031618.g004

Caption as it should appear with typos corrected:

Figure 4. Examples of altered brain scaling relationships.
Solid and dashed lines in (A–C) indicate hypothetical standardized major axis (SMA) scaling relationships of brain region volume (y variable) with brain size (x variable). (A) Altered slopes (β1 and β2), which preclude further scaling analyses using these methods. (B). Groups share a common scaling slope and y-intercept (y1) but average brain size differs between groups (x1 and x2), producing an x-axis shift. (C) Groups share a common scaling slope and average brain size (x1) but y-intercepts (y1 and y2) are shifted, producing a grade shift. (D) Solid lines represent actual SMA scaling regressions of mushroom body volume versus remainder-of-central-brain volume (ROCBV) for mature P. pilifera minors (circles) and mature P. pilifera majors (squares), representative of a grade shift accompanying a shift along the x-axis. Dashed line in (D) indicates slope of 1 (isometry) for reference.
doi:10.1371/journal.pone.0031618.g004