THE ADVANCE OF SCIENCE 



101 



any such connection in the case of vertebrates of a 

 more definite character than we admit in the case of 

 starfishes, shell-fish, and insects. All these groups are 



FIG. 20. 



Drawings by Professor Grassi, of Rome, of the young of the common 

 Eel and its metamorphosis. All of the natural size. The uppermost figure 

 represents a transparent glass-like creature which was known as a rare 

 "find" to marine naturalists, and received the name Leptocephalus. 

 Really it lives in vast numbers in great depths of the sea five hundred 

 fathoms and more. It is hatched here from the eggs of the common Eel 

 which descends from the ponds, lakes, and rivers of Europe in order to 

 breed in these great depths. The gradual change of the Leptocephalus 

 into a young Eel or "Elver" is shown, and was discovered by Grassi. 

 The young Eels leave the great depth of the ocean and ascend the rivers 

 in immense shoals of many hundred thousand individuals, and wriggle 

 their way up banks and rocks into the small streams and pools of the 

 continent. 



The above figures were published by Professor Grassi in November, 

 1896, in the Quarterly Journal of Microscopical Science, edited by E. Ray 

 Lankester and published by Churchill & Sons. 



