Alaninuiiia. 6i 



Kiikeiithal's opinion seems to be that the increase of teeth 

 amongst the Pinnipedia, whether by reduplication or by the addition 

 of new teeth, is due to a tendency to lengthen the jaw amongst a 

 group of animals wdiose development is still going on, and to whom 

 in the execution of their main object in life, namely the capture of 

 fish, such a lengthening would be useful. 



He finds a parallel between the reduplication of the teeth of 

 Ommato]}1wca and the development of teeth in young Whalebone 

 Whales, in which his studies have shown that, while the rudimentary 

 cheek-teeth of the youngest embryos are many-cusped, those of older 

 embryos are single- cusped, and occasionally reduplicated. 



With the earlier portion of Dr. Kiikenthal's remarks few, no 

 doubt, will be found to disagree. The suggestion that a new tooth 

 may arise either as an offshoot of one already in existence or as a 

 new and independent organ is indeed not without probability. 

 When, however, he comes to deal with increase of the teeth amongst 

 the Pin7iipedia, he gives vent to suggestions which, however probable 

 they may have appeared at the time when they were written, 

 certainly do not apply to Ommatophoca as we now know it in the 

 light of Dr. Racovitza's description. According to that naturalist, 

 the animal never catches fish ; its jaw is extremely short and feeble, 

 and there is no evidence whatsoever to justify us in supposing that 

 a lengthening of the jaw would be either useful or probable in the 

 future. Whatever applications Dr. Kiikenthal's remarks may bear 

 to other Pinnipeds they can have no meaning whatsoever as applied 

 to Ommatoplioca. 



To consider the specimens once more, the most striking charac- 

 teristic of the series is, to my mind, not any possible increase or 

 reduction of the teeth, but the exceeding variation which they 

 exhibit. The most noticeable feature of this variation is certainly 

 its quantity : its quality (for a knowledge of which we are so largely 

 indebted to Mr. Bateson) may be found exhibited in numerous other 

 instances amongst the Mammalia. As compared with this variation, 

 questions of increase or decrease of teeth are evidently, in this case, 

 even if proved, subsidiary. The one thing obvious is that we have 

 in Ommatophoca an animal in which the dentition is, whether in 

 number of teeth, in their size or form, vastly more variable than it 

 is in any other known Heterodont Mammal. 



Recent investigation has shown that teeth, like every other 

 character, are subject to variation. They are not the entirely stable 

 organs they were at one time believed to be. Yet no instance of 

 instability so remarkable as that of Ommatophoca has, I believe, been 



