OP A HIGHER FOKJVL OF LIFE ON A LOWER FOEM. 429
water into them whilst struggling with a drowning prey, he thought this exclusion was brought about mainly by the closure of the ex- terior nostrils, since if these were closed, the nasal passage being filled with air and not a vacuum, water could not enter the poste- rior nares by the mouth. It was, however, the exclusion of water from the glottis and not from the posterior nares which is important. The narial passages and trachea do not form a continuous, but an interrupted tube, without the admirable contrivance which Cetaceans have of a conical larynx, which can be raised and plugged into the palato-nares ; for the upper opening in Crocodiles is a simple slit, not particularly prominent, and not capable of such exact adjustment to the palato-nares as in Whales.
Mr. Hicks asked if, with the cessation of the existing circum- stances, the acquired structural modifications would cease and the Crocodile go back to its primitive form.
Sir Philip Grey-Egerton observed that in the beginning of the paper the author noticed the modifications of structure of mammals adax)ted to the surface of the earth, the splay-footed ones moving better over the soft surface ; but it must not be overlooked that with these coexisted narrow-footed forms. He thought that the author should have shown that the splay-footed ones alone existed then.
Prof. Owen, in reply to Dr. Meryon, said that he was gratified to find that his paper had called forth the remarks to which he had listened with pleasure from his old and esteemed friend. It would be seen, however, that his paper was teleological rather than evolutionist, indi- cative of how the structures characterizing the Neozoic Crocodilia would operate in giving them advantage in the capture of terrestrial prey. Wo doubt a reference had been made to the Lamarckian view of the conditions under which such modifications of structure might be acquired, and the requirements, by an objector, of the intermediate stages of the change from the amphiccelian to proccelian types was referred to. Instances of that character were few, but might be cited. The Mesozoic GoniopJiolis, e. g., with broad thick jaws, wavy alveolar tract, and large and unequal teeth, combined these Neozoic characters with the Mesozoic large, horizontal, advanced palato-nares. The existing Gavial retains the long narrow jaws, straight alveolar tract, numerous small and similar-sized teeth, with the small, sub- vertical, posteriorly placed palato-nares characteristic of Neozoic Crocodiles. Considering the enormous lapse of time between the Wealden and Eocene periods, it may reasonably be expected that many more of these " missing links " will be found ; and one object in our allusion to them in this paper, honoured by Dr. Meryon's remarks, was the additional stimulus it held out to paleontologists and intelligent collectors of fossils to researches which might be re- warded by such discoveries.
With regard to that part of Mr. Hulke's objection bearing on the scutal characters of Mesozoic and Neozoic Crocodiles, it is true that, as Natterer has pointed out, the ventral as well as the dorsal scutes of the Jacquari are ossified ; but those scutes are less firmly con- nected together; they are united neither by the peg-and-groove
