4o8 DISCOVERY REPORTS 



Photomicrographs of the condition in a Fin female of 21-42 m. (No. 3178) are shown 

 in Plate V, figs. 1-3. In this whale pieces of the vertebrae were chipped off with the 

 axe, decalcified in formalin and nitric acid, and sectioned with the freezing microtome. 

 The sections were stained by Schmorl's picrothionin method. 



The notes made upon the plan were as follows : 



2nd-3rd thoracic ... ... Epiphyses not fused to centra; separating 



cartilage layer very thin 

 15th thoracic-ist lumbar ... Epiphyses fused to centra. Join visible 

 I3th-i4th lumbar ... ... Epiphyses fused to centra. No sign of join 



The cartilage layer, plainly continuous in the anterior thoracic vertebrae, is in process 

 of invasion by bone cells in the posterior thoracic region, and has completely dis- 

 appeared at the posterior end of the column. 



A second series from a Fin female of 22-0 m. (No. 3196) is given in Plate V, 

 figs. 4-6. The vertebrae examined and the notes made on the plan were as follows: 



2nd-3rd thoracics ... ... Epiphyses unfused. Thin cartilage 



4th-5th lumbars ... ... Epiphyses unfused. Thin cartilage 



15th lumbar-ist caudal ... Epiphyses fused 



The staining of these sections was not as successful as in the first series. Too long 

 immersion in picric acid had the effect of masking the thionin stain, with the result 

 that the cartilage appears lighter than the bone. The different stages of invasion, how- 

 ever, can still be clearly seen. 



Nearly 200 sexually mature female Fin whales were examined, and from these it may 

 be said that, at least as far forwards as the 3rd or 4th thoracic vertebra, ankylosis pro- 

 ceeds from the posterior end of the column. In one only (No. 3 181) did the observa- 

 tions suggest that ankylosis might be completed in the posterior thoracic region rather 

 than at the anterior end of this series. The full results are given in the table of records 

 on pp. 422-434. In male Fin whales and all Blue and Sei whales results similar to those 

 given above were found. 



It is interesting to note that fusion from the posterior end of the column was observed 

 by Barrett-Hamilton (see Hinton, 1925), who, in his notes on the Humpback (p. 79) 

 mentions "vertebral epiphyses fusing but visible in lumbars, thoracics not fused and 

 thin" : among Fin whales (p. 105) and Blue whales (p. 139) he gives several examples of 

 lumbar vertebrae fused while the thoracics were distinct. 



On the advice of Sir Sidney Harmer a detailed examination was made of the skeletons 

 of whales and dolphins in the British Museum (Natural History) to determine the state 

 of the cervical epiphyses and vertebrae during the process of ankylosis. More than 

 ninety specimens, including a few seen at the Zoological Museum at Cambridge, were 

 examined, and although in some of them the epiphyses were free throughout and in 

 others physical maturity had been reached and the epiphyses were completely ankylosed, 



