_ao._ Aorta. _cv._ Cardinal vein. _gl._ Glomerulus. _gr_1. First groove of
head-kidney. _gr_2. Second groove of head-kidney. _gr_3. Third groove of
head-kidney. _ge._ Germinal epithelium. _mrb._ Malpighian body. _me._
Mesentery. _md._ Müllerian duct. _r_1. First ridge of head-kidney. _r_2.
Second ridge of head-kidney. _r_3. Third ridge of head-kidney. _Wd._
Wolffian duct. _x._ Fold in germinal epithelium.