PHYLOGENY OF THE PALZOGNATHA AND NEOGNATHZ. 259 
fundamentally from that of the Neognathw, since in these last it opens by a more 
or less constricted aperture into the general cavity of the cloaca, whilst in the 
Struthiones the exact opposite was the case, the cloaca opening into the bursa. 
* From this..... it will be at once evident that the cloaca does not open directly to 
the outer surface, but indirectly through the bursa by means of its large posterior and 
inferior aperture.” 
I find myself unable to confirm this point, and I think the accompanying figure will 
justify me. The only difference which I can see between the Palwo- and Neognathw in 
this particular is that in the latter the bursa opens into the roof of the proctodeum by 
means of a minute aperture, in the former it opens by a very large one, so large as to 
absorb nearly the whole roof of the proctodeum. 
When these parts are dissected from spirit-specimens, in which hardening has taken 
place én situ, Forbes’s description seems to be amply verified, as I can testify. The 
accompanying figure was made from a specimen in which the hinder end of the gut 
had been removed soon after death, the cloacal aperture set widely open, and the 
whole plunged into formol and left for two or three days. The wall of one side was 
then removed and the true relations revealed. 
The function of the bursa is yet unknown. 
c. CopuLATORY ORGANS. 
The Paleognathe all possess a well-developed copulatory organ. 
That of Struthio is a solid grooved organ containing erectile tissue and resembling 
very nearly that of the Chelonia and Crocodilia. It can be retracted into a 
pouch in the floor of the proctodeum. The m. protractor penis receives a slip from 
the transversus analis, which descends from the pelvic bones. A pair of retractores 
penis arise from the pelvis and are attached to the ventral aspect of the middle portion 
of the organ. 
In the remaining Palewognathe the penis resembles that of the Anseres amongst 
the Carinatw, being evertible and more or less markedly spirally twisted and grooved 
dorsally. 
The copulatory muscles of the Palwognathe, Dr. Gadow [24] points out, differ 
from those of the Neognathw, inasmuch as the latter are derived from the sphincter ani 
solely, whilst in the Palwognathw they are partly differentiated from muscles which are 
still attached to the pelvis, and are therefore skeleto-genital. 
DEVELOPMENT. 
The egg of the Palwognathe, save in Apteryx and perhaps the Crypturi, differs from 
that of the Weognathw in that the pore-canals are branched. In Apteryz, as in the 
Neognathe, they are unbranched. 
In Struthio, according to Nassonovy [64], and Apterya, according to Parker [71}, an 
