56



Mr. P. W. Pycraft,



of characters distinguishing the Cuckoos and Touracous from

the Hoatzin, he defines the young of the former as perfectly

naked and nidicolous (echte nackte nesthocker).


Thus then, Mrs. Johnstone’s success proves to be one of

unusual importance, for, apart from its bearing on questions of

aviculture, it has thrown new light on the difficult problem

of classification.


II. Pteryeosis.

a. The trunk.


From a reference to the figure in Mrs. Johnstone’s paper it

will be apparent that the young bird, at one month old, is still

completely invested in nestling down save only the wings and

tail, where contour feathers have made their appearance. An

examination of the skin however shows that a few feathers have

begun to sprout from the scapular tracts and from the back of the

neck. The rest of the body is clothed in a short black down

sparsely distributed.


It is not easy to exactly define the form of the several

feather tracts in this nestling, and the task of tracing these is

rendered the more difficult in the absence of an adult for

comparison.


But the head, neck, and upper part of the spinal tract can

be clearly made out. The spinal tract however, on the middle of

the back, spreads out so as to extend downwards and ultimately

blend with the femoral tract—a very primitive character.


The ventral tract, which we may reckon for our present

purpose as commencing at the base of the lower jaw, is at first

ill-defined. There is no interramal space as usual. On the

middle of the under surface of the neck it widens considerably,

and then, sending off a branch to the shoulder, is continued

backwards in the form of a broad outer tract, terminating at the

level of the hinder border of the sternum : and a narrow feebly

developed, and ill-defined median tract, which runs backwards

and downwards to meet its fellow of the opposite side in front

of the cloaca.


The crural or leg tract is unusually well-developed. No

down appears on the apteria or spaces between the tracts.



