12 



Professor Flower 



[May 25, 



more remarkable. In all known Cetacea (unless Platanista be really 

 an exception) a pair of slender bones are found suspended a short 

 distance below the vertebral column, but not attached to it, about the 

 part where the body and the tail join. In museum skeletons these 

 iDones are often not seen, as, unless special care has been taken in the 

 preparation, they are apt to get lost. They are, however, of much 

 importance and interest, as their relations to surrounding parts show 

 that they are the rudimentary representatives of the pelvic or hip 

 bones, which in other mammals play such an important part in con- 

 necting the hind-limbs with the rest of the skeleton. The pelvic arch 

 is thus almost universally present, but of the limb proper there is, as 

 far as is yet known, not a vestige in any of the large group of toothed 

 w^hales, not even in the great Cachalot or Sperm Whale, although it 

 should be mentioned that it has never been looked for in that animal 

 with any sort of care. With the Whalebone Whales, however, at 

 least to some of the species, the case is different. In these animals 

 there are found, attached to the outer and lower side of the pelvic 

 bone, other elements, bony or only cartilaginous as the case may be, 

 clearly representing rudiments of the first and in some cases the 

 second segment of the limb, the thigh or femur, and the leg or tibia. 

 In the small Balcenoptera rostrata a few thin fragments of cartilage, 

 imbedded in fibrous tissue attached to the side of the pelvic bone, con- 

 stitute the most rudimentary possible condition of a hind-limb, and 

 could not be recognised as such but for their analogy with other allied 

 cases. In the large Rorqual, Balcenoptera musculus, 67 feet long, pre- 

 viously spoken of, I was fortunate enough in 1865 to find attached 

 by fibrous tissue to the side of the pelvic bone (which was sixteen 

 inches in length) a distinct femur, consisting of a nodule of cartilage 

 of a slightly compressed, irregularly oval form, and not quite one 

 inch and a half in length. Other specimens of the same animal 

 dissected by Van Beneden and Professor Struthers have shown the 

 same ; in one case, partial ossification had taken place. In the genus 

 Megaj^tera a similar femur has been described by Eschricht ; and the 

 observations of Eeinhardt have shown that the Greenland Eight 

 Whale {Balcena mijsticetus) has not only a representative of the femur 

 developed far more completely than in the Eorqual, being from six 

 to eight inches in length and completely ossified, but also a second 

 smaller and more irregularly formed bone, representing the tibia. 

 Our knowledge of these parts in this species has recently been 

 greatly extended by the researches of Dr. Struthers, who has pub- 

 lished in the ' Journal of Anatomy ' for 1881 a most careful and 

 detailed account of the dissection of several specimens, showing the 

 amount of variation to which these bones (as with most rudimentary 

 structures) are liable in different individuals, and describing for the 

 first time their distinct articulation one with the other by synovial 

 joints and capsular ligaments, and also the most remarkable and 

 unlooked-for presence of muscles passing from one bone to the other, 

 representing the adductors and flexors of mammals with completely 



