The whole structure of this huge anthropoid ape is not merely very similar to that of man, but it is substantially the same. “The same 200 bones, arranged in the same way, form our internal skeleton; the same 300 muscles effect our movements; the same hair covers our skin; the same groups of ganglionic cells compose the ingenious mechanism of our brain; the same four-chambered heart is the central pump of our circulation.” The really existing differences in the shape and size of the various parts are explained by differences in their growth, due to adaptation to different habits of life and unequal use of the various organs. This of itself proves morphologically the descent of man from the ape. We will return to the point in Chapter XXIII. But I wanted to point already to this important solution of “the question of questions,” because that agreement in the formation of the embryonic membranes and in fœtal circulation which I have described affords a particularly weighty proof of it. It is the more instructive as even cenogenetic structures may in certain circumstances have a high phylogenetic value. In conjunction with the other facts, it affords a striking confirmation of our biogenetic law. Fig.208. Female gorilla. Fig. 208—Female gorilla. (From _Brehm_). Fig.209. Male giant-gorilla (Gorilla gigas), from Yaunde, in the interior of the Cameroons. Killed by H. Paschen, stuffed by Umlauff. Fig. 209—Male giant-gorilla (_Gorilla gigas_), from Yaunde, in the interior of the Cameroons. Killed by H. Paschen, stuffed by Umlauff. Chapter XVI. STRUCTURE OF THE LANCELET AND THE SEA-SQUIRT