498

464

by the following facts. the greater number of the sacro-vertebral attachments of the
chick's ilium, in whatever degree enlarged and fossilized, would lead me to refer it
to the avian, not the reptilian type. I should also note the presence in the ischium
of an obturator process wanting in the Dinosaur, and the absence of a pectineal process
in the chick's pubis, present in the bone of the Dinosaur, and, further, the paral-
lelism and backward extension of both pelvic bones in the chick, contrasted with
their downward extension and divergence in the Dinosaur.

In further testing the embryological ground evoked, I find the differences between
the half-hatched chick and the full-grown Dinosaur grow and multiply as the com-
parison proceeds. the distal epiphysis of the chick's tibia is not only larger and
more complex than that of the Dinosaur, but it articulates, not with one of four tarsal
bones, but with the proximal epiphysis of a compound metatarsus. The fibula of the
chick ends in a point at some distance above the ankle-joint, whilst in the Dinosaur its
distal end expands, is parallel with that of the tibia, and has an epiphysis which arti-
culates with a calcaneum 1. I should further note the backward direction of the inner-
most or first toe (1.) in the chick, and contrast it with the parallel position of that toe
with the forwardly directed second toe in the Dinosauria, before committing myself to
a reference of an embryo bird to that order. If the entire skeleton of an immature
bird of any order, whether volant or not, were enlarged to the dimensions of that of a
Dinosaur, the characters of the few dorsal and caudal vertebrae, of the many cervical
vertebrae, and of the skull, the absence of an anterior pair of limbs with fore paws
organized to be applied to the soil and to take their share in the support and progression
of a long and bulky trunk, with the massive head of a Dinosaur, would be decisive
against the reference of such imaginary gigantic chick to any known representative of
a terrestrial order of reptiles. In no birds are the sacral vertebrae so few as in Dino-
sauria ; and in those birds which, from the embryonal proportions of the wings, their great
size and terrestrial habits, are adduced to exemplify Dinosaurian origin and affinity,
the number of the sacral vertebrae ranges from seventeen (Dinornis) to twenty (Struthio).
I may refer to my 'Monograph' above cited for an analysis of the grounds of ascription
of a bipedal mode of locomotion to the Dinosauria, in further support of the idea of
their ancestral relationship to winged birds through the terrestrial gigantic forms of the
feathered class.

In now submitting the grounds on which the view of the origin of the flightless or
wingless birds by way of degeneration from antecedent winged forms is preferred, I
fully appreciate the limited application of the Lamarckian hypothesis in the exposition
of the secondary law of the origin of organic species.

But I would add that, without knowing or pretending to know the ways of operation
of such secondary cause, the vast increase of knowledge-stores of biological phenomena

1 See 'Monograph on the Fossil Reptilia of the kimmeridge Clay ;' in the volume of the Palaeontographical
Society issued in 1875, p. 84, fig. 16, "Dinornis chick and Scelidosaur."