6 ARKIV FOR ZOOLOGI. BAND 7. N:0 Z. 



As it appeared to be of interest to ascertain whether 

 the development of accessory cusps on the teeth of the White 

 whale as originally seen by True, and then, as is described 

 above, amply confirmed by the present author was a common 

 or even constant occurrence, T wrote to my friend Mr. H. 

 WiNGE and asked him to kindly examine the skulls of thia 

 species in the Zoological Museum of Copenhagen. Mr. Winge 

 Avas good enough to do so and then wrote a letter to me 

 about the result of his examination. Out of this communi- 

 cation I take the liberty of quoting some notes. In a skull 

 of a foetus or newbor» White whale in which the teeth w^ere 

 left only on the right side Winge found »on the tw^o or three 

 hindmost teeth» traces of two vertical furrows on the inner 

 side of the crown, and the hindmost tooth of the lower jaw 

 was notched in front of the uppermost cusp. In another 

 young specimen one of the middle teeth on either side of the 

 lower jaAv was notched as w^ell behind as in front. In three 

 more similar skulls several teeth showed more or less plainly 

 the two vertical furrows on the inner side, and some were 

 more or less faintly notched. Among the adult skulls of 

 White whale one was found in which the second tooth from 

 behind on either side of the upper jaw had quite a consider- 

 able notch in the posterior margin of the crown, and the 

 hindmost upper tooth on either side of the same specimen 

 appeared to have a similar shape, although the latter still 

 were mostly hidden in the jaw. 



x^lthough the material in the Copenhagen museum does 

 not appear to be quite as favourable as my own, it confirms 

 the observations and statements made by True and the 

 present writer. A great variation takes place w4th regard to 

 the degree of development of the accessory cusps, but this 

 is no wonder, because not only these small accessory cusps 

 themselves but the whole crowns of the teeth are to be re- 

 garded as rudiments, as has been set forth above. They must 

 therefore be subjected to the general rule that rudimentary 

 organs vary to a considerable degree in their development. 



With regard to the shape of the main part of the teeth, 

 that is the roots, it may be said that they are to begin with 

 almost cylindrical, although as a rule more or less curved. 

 In the skull with a basicranial length of 47V2 cm. they are 

 also almost cylindrical in the upper jaw. even if the träns- 



