Embryology and Growth of Fishes 147 



Some fresh-water fishes are very fragile, dying soon in the 

 air, often with injured air-bladder or blood-vessels. They will die 





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Fig. 112. — Alhula vulpes (Linnaeus). Transformation of the Ladyfish, from the 

 translucent, loosely compacted larva to the smaller, firm-bodied young. Gulf 

 of California. (After Gilbert.) 



even sooner in foul water. Other fishes are extremely tena- 

 cious of life. The mud-minnow (Umbra) is sometimes ploughed 

 up in the half -dried mud of Wisconsin prairies. The related Alas- 



