OF ARTS AND SCIENCES. 127 



Fig. 11. The tail has now the shape of that of the adult; the merest trace of 

 the embryonic caudal remains. 

 „ 12. Fig. 11 somewhat magnified, to show the cartilages supporting the 

 permanent and the accessory fin-rays of the tail, as well as the 

 urostyle with last ossified vetebra. 



The young Flounder of Fig. 1 measured 6™"°- in length ; that of Fig. 12 meas- 

 ured IS""*^-; the whole change of the tail, from the straight notochord of 

 Fig. 1 to the rounded tail of Fig. 12, took place in about three weeks, judging 

 from the specimens fished up. 



PLATE II. 



Tails of Embryos of Young Fishes. 



-4. Atherina, respectively 5"^-, 9™™-, 10™™-, ll™m- long. 

 Batrachus. 9™™- long. 

 Lumpus. 4™™- long 

 Ctenolabrus. 6™™- long. 

 Poronotus. 7™™- long. 



Young Lophius with straight notochord. About 5™™- long. 

 Heterocercal tail of young Lophius. 20™- long. 

 Fleshy pectoral of same, seen from the side. 

 Same seen from above. 

 Figs. 13, 14. Gasterosteus. 



„ 16, 17, 18. Phycis. Fig. 16 f: 3™™-, 8™™-, 15™™-. 

 Fig. 19. Cod. 20™™- long. 

 „ 20 and Fig. 18. Magnified. (Phycis.) 



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