Blood cells; Erythrocytes, Leukocytes, and Platelets (thrombocytes).
“Normoblasts” are the immediate precursor to erythrocytes (red blood cells) - they’re essentially an erythrocyte that still maintains a cell nucleus.
The “transitional form” is a transitional white blood cell.
Normal Histology, With Special Reference to the Structure of the Human Body. George A. Piersol, 1910.