command. They show successive stages from the time the embryo is first outlined, and, taken in their entirety, they cover a wide range of stages.
His observations on the development of the heart, comprising twenty figures, are the most complete. He clearly illustrates the aortic arches,—those transitory structures of such great interest as showing a phase in ancestral history.
He was also the first to show by pictures the formation of the head-fold and neural groove as well as the brain vesicles and eye
pockets. His delineation of heart, brain and eye vesicles are far ahead of those illustrating Wolff's 'Theoria Generationis' made nearly a hundred years later. But Wolff rose to a higher level in his later work on the development of the intestine, and produced some figures better than any of Malpighi's.
The original drawings for 'De Ovo Incubato,' still in possession of the Royal Society, are made in pencil and red chalk. They far surpass the reproductions in finish and accuracy. In looking them over in 1902, I noticed four aortic arches represented in one figure where the engraver has shown only three.
The portrait of Malpighi shown in Fig. 3 is taken from his Life
