PterylograjiJnj of the Hoatzin. 369 



contour-feathers. There seems to be very good reason for 

 believing this may be really the case. In the nearly ripe 

 embryo, it will be remembered, the pt. spinalis and femoralis 

 appear to be confluent, whilst in the adult, as a reference to 

 the figures (PI. IX.) will show, the actual distribution of the 

 contour-feathers in this region has become much restricted. 

 The semiplumes distributed in the space dividing the femoral 

 from the spinal tract probably represent degenerate contour- 

 feathers. It remains to be seen whether, on examination of 

 perfectly fresh specimens, these semiplumes correspond to 

 the embryonic feathers in the same region. In my speci- 

 mens many of these feathers (semiplumes) have been lost, so 

 that it is difficult, if not impossible, to settle this point now. 



Mr. Beddard's paper (1) contains one or two statements 

 which I cannot entirely corroborate. As touching the spinal 

 tract, for instance ; although in the spirit-specimens the 

 pt. spinalis is not so sharply defined as in my figures, inas- 

 much as there are no boundary lines, such as I have drawn, 

 yet we can scarcely say that the " dorsal surface is feathered 

 all over with larger feathers here and there.^^ Again,, as 

 touching the ''median apterion" [apt. mesogastrm). In my 

 adult specimens this is certainly not " sparselj^ feathered/' 

 nor can it be said that the '^ median apterion does not .... 

 commence until the carina sterni, .... its breadth being 

 precisely that of the carina.'^ The nestlings, however, — and 

 the nearly ripe embryo — seem to support Beddard's state- 

 ments ; but in hoAv far this is actually the case remains to be 

 seen, inasmuch as it is an almost hopeless task to difi"erentiate 

 between down- feathers (phmiula) and neossoptiles with any- 

 thing like precision enough to settle the question, and hence 

 this must be left for a further examination of freshly-killed 

 specimens. It is quite possible that, these being small and 

 probably semiplumous feathers, they have fallen out in the 

 adult submitted to me. I do not find that the lateral ventral 

 tracts unite with each other in front of the cloacal aperture, 

 or that they are connected with the femoral tracts by scat- 

 tered feathering. 



In the nestling Beddard almost distinguishes between the 



SER. VII. VOL. 1. 2d 



