PHTLOGENY OF THE PAL^OdNATH^ AM) NEOGNATILE. 259 



fundamentally from that of the Neogitatha, 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 7wt open directly to 



the outer surface, but indirectly tlirough the bursa by means of its large posterior and 

 inferior aperture." 



I tind 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 Neognathce in 

 this particular is that in the latter the bursa opens into the roof of the proctodseum 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 proctodaeum. 



When these parts are dissected fi-om spirit-specimens, in which hardening has taken 

 place in 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 tliree days. The wall of one side was 

 then removed and tlie true relations revealed. 



The function of the bursa is yet unknown. 



c. C()Pui>AToRv Organs. 



The Palavgnatlue all possess a well-developed copulatory organ. 



That of fStruthio is a solid grooved organ containing erectile tissue and resembling 

 very nearly that of the Chelonia and Crocodi/ia. It can be retracted into a 

 pouch in the floor of the proctodaeum. The ni. protractor penis receives a slip from 

 the transversus analis, which descends from the pelvic bones. A pair of retractores 

 j)enis arise from the pelvis and are attached to tlie ventral aspect of the middle portion 

 of the organ. 



In the remaining Faloognatluf the penis resembles that of the Anseres amongst 

 the Carinatu', being evertible and more or less markedly spirally twisted and grooved 

 dor sally. 



The copulatory muscles of the Palceognatha', Dr. Gadow [24] points out, differ 

 from those of the Neogiiatluc, inasmuch as the latter are derived from the sphincter ani 

 solely, whilst in the Pahtognatlia- tliey are partly differentiated from muscles which are 

 still attached to the pelvis, and are therefore skeleto-genital. 



DEVELOPMENT. 



The egg of the Paheognatha', save in Apteryx and perhaps tlic Crypturi, differs from 

 that of the Neognatlue in that the pore-canals are branched. In Apiteryx, as in the 

 Neognathie, they are unbranched. 



In Struthio, according to Nassonov [64], and Apteryx, according to Parker [71], an 



