POSTSCRIPTUM. 



After this publication haä been completed in December 1918, except the 

 reproduction of the illustrations which proved a tedious process, I recently 

 received for perusal the „Memoirs of the American Museum of Natural 

 History", New Series, Vol. I Part VI, March 1916. 



This publication contains two monographs on Balaenoptera borealis 

 Lesser by Mr. Roy Chapman Andrews, and Mr. H. von W. Schulte, the latter 

 author treating of the anatomy of a foetus. 



It being a young foetus it has to be born in mind that many characters 

 observed in this embryo may be far more primitive and less specialised than 

 the corresponding traits in the adult animal. 



Considering that the dentate Zeuglodon Owen, an extinct Cetacean, 

 is generally looked upon as one of the ascendants of the living species of 

 Cetaceans, there is no matter for surprise in the fact that teeth are still found 

 in baleen-whales in embryonic stages. 



In connection with the fact that the maxillary-articulation was originally 

 designed for mastication, it is quite to be expected that in the embryonal 

 phases the articular processes of the lower jaw, should approximate more 

 closely to the prototype of the whale than is the case in the adult creature. 



In the Balaenoptera-skeleion at Buitenzorg the length of the inferior 

 maxilla measured externally amounts to 620 c.M., whereas the declining 

 articular extremity is comparatively small. 



On page 483 of the Memoirs of the American Museum of Natural History 

 just quoted, the length of the lower-jaw measured externally is stated to be 

 7,5 C.M., against an height of 1.35 c.M. for the articular extremity. This 

 latter measurement is very great in proportion to the length of the lower-jaw. 

 Moreover the condyle of the processus articularis inclines upwards, and as 

 a result the whole organ approaches more nearly to the primitive maxillary 

 articulation. 



From the following words of the author (H. von W. Schulte) it appears 

 however, that a normally functioning articulation is out of the question; 



„I could make out no synovial cavities, but the tissue adjacent to the 

 bones was loose and easily stripped off". 



The monographs by Messrs. Andrews and Schulte being of a more 



