CULTURE OP THE SHAD. 159 



eye, which fills proportionately at least four times more 

 space than in the adult. The choroid coat, not yet closed 

 below, partly encircles the crystalline lens, above which 

 may be distinguished a clear space, which is a portion of 

 the vitreous humor. The form of the brain may already 

 be distinguished, especially when fore-shortened from the 

 front. It is probable that the pectoral fin already exists, 

 but, from the extreme transparency of the tissues, its out- 

 line could not be caught. From the well-marked nuchal 

 bow, the flattened body tapers gradually to a fine point, and 

 is bordered, above and below, by an embryonic dorsal and 

 ventral which spread into a spatula-like caudal fin, and it 

 should be observed, that neither in this stage nor in the 

 newly-hatched, does there exist any unevenness of the 

 margins of these fins, that should indicate their approach- 

 ing separation ; whereas, the newly-hatched salmon already 

 shows very distinct dorsal, adipose, caudal, anal, and ven- 

 tral fins ; and the little Coregonus, though less advanced in 

 this respect, shows plainly the boundaries of these organs. 

 Near the base of the caudal is now to be seen the end of 

 the alimentary canal, passing at an angle across the breadth 

 of the fin. The heart may be observed beating, and the 

 embryo itself moves itself round and round within its 

 prison, by a series of convulsive jerks. This motion is 

 called by the breeders, 'life in the egg.'* 



* In this stage Green succeeded in keeping eggs alive in damp 

 moss for six days, in a low temperature. But they are very hard 

 to transport long distances, and cannot be hatched in cold water. 



