74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. ^2 



and in the shortening of the braincase, but cannot prove that asym- 

 metry would be the necessary result of these causes. 



Lillie (section The asymmetry of the Odontocete skull, in Observa- 

 tions on the anatomy and general biology of some members of the 

 larger Cetacea, Proc. Zool. Soc. London, 1910, vol. 2, pp. 781-783, 

 with figure) shows that the phar3mx in Physeter is asymmetrical, 

 divided by the projecting larynx, which is strongly displaced to the 

 left, into a more spacious right and a narrower left section to accom- 

 modate the passage of food. In this circumstance should be found 

 the source of the asymmetry of the face ; why, is not further explained. 



Steinmann starts from Kiikenthal's assertion about the asymmetry 

 in the caudal fin. KiJkenthal had said nothing as to the cause of this 

 crookedness, but Steinmann believes he has found it in the supposed 

 fact that whales originated from Ichthyosaurs and other marine 

 reptiles with a vertical fin, and that on its way to the horizontal posi- 

 tion the fin has come to rest obliquely. 



Kiikenthal is doubtless the one who has come nearest to the truth. 

 However, there are numerous objections to be raised against his 

 explanation. It cannot be said with any degree of correctness that 

 the skull in the whalebone whales has an asymmetrical face. A series 

 of skulls is before me, representing Balccna, Balccnoptera and Megap- 

 tera. Such asymmetry as can perhaps be shown here and there is 

 similar to that which is found in most mammals. I myself have 

 seen many cetacean embryos (in alcohol), representing both whale- 

 bone whales and odontocetes (of the former I have examined in this 

 connection embryos of 3 Balccnoptera rostrata, 2 B. musciilus, 5 

 Megaptera boops, of the latter numerous embryos representing the 

 genera Delphinapterus, Monodon, Prodelphinus, Delphinus, Lageno- 

 rhynchus, Glohiceps, Phoccena, Neomeris; I have been content with 

 examining the tails externally, I have not cross-sectioned them), but 

 I have not been able to convince myself of the presence of oblique- 

 ness in the tail which did not appear to find its explanation in artificial 

 pressure. I have also seen various adult newly dead cetaceans, both 

 whalebone whales and toothed cetacea of different kinds. It is true 

 I did not expressly examine them to observe obliqueness of the tail, 

 but I cannot recall the slightest evidence of its existence. Neither 

 can anything be detected in the numerous photographs of whales that 

 are before me. That obliqueness of the tail can actually be present 

 appears to be proved by Kiikenthal's figure of a cut ofif tail of Balccn- 

 optera, which shows the flukes placed obliquely in relation to the 

 caudal vertebrae ; but it must probably be an exception. Even if it 



