1224 



MR. F. R. WELLS ON THE MORPHOLOGY OF THE 



The palatal cartilage is comparatively larger in cross-section, 

 and from its posterior end there runs a thin strip of cartilag-e 

 to meet the hyomandibular mass at its anterior end. It is 

 important to notice that this fusion is entirely secondary, and, 

 as pointed out above, the upper ja-w grows hack from the 

 front. 



The hyomandibular mass of cartilage has grown considerably, 

 being now nearly half as long as the whole chondrocranium. 

 The articulation with the cranium is as before, the stylohyoid 

 and the forward growing piece of cartilage, just in front of it, are 

 even more conspicuous. Just in front of the base of this forward 

 growing part tlie hyomandibular mass forms a narrow neck, and 



Text-figure 8. 



Ventral views of ethmoid plate in the 10 mm. and 30 mm. Stages. X 30. 



spreads out again further forward. From its anterior end on top 

 it sends forward the thin strip to meet the uppet jaw, and 

 immediately below this there is a small protrusion which articu- 

 lates with Meckel's cartilage. At the articulation there is a 

 large upward growth from Meckel's cartilage, otherwise it is 

 unchanged. 



The two foramina of the Vllth nerve (facial) are unchanged. 



e. The 40 mm. Stage. 



This account is based 0]i the studj^ of transverse sections of a 

 40 mm. specimen of the Herring and on a reconstruction of it 

 (text-fig. 9). 



The whole chondrocranium has considerably increased in height 

 without a Yerj marked change in length. 



The anterior end of the ethmoid plate and the median ridge 

 show little change, except in the formation of the anterior eye- 

 muscle canal ; the rostrum is more pointed. The epiphysial bar 

 is unchanged ; the post-orbital processes have become compara- 

 tively more massive, and from the ventral side of their anterior 



