COMING ON SHORE 181 



have a motile tongue, which in the frog is fixed in front and 

 not, like ours, behind, and can be shot out at a great distance 

 to catch their insect food. 



Again, amongst Amphibia, we for the first time come 

 across a vertebrate voice. The serenading of the frog recorded 

 by Aristophanes is produced by the passage of air being 

 breathed out through vocal chords stretched tight in the 

 larynx. In Aristophanes' play of the Frogs their voices, which 

 are very primitive, are reproduced by the following line: 



Brekekekex, ko-ax, ko-ax, 



In Rogers' translation of this comedy there is an interesting 

 note, which I here reproduce: 



The croak of a frog has been one of the best means of informing the 

 modern world of the manner in which the ancient Greeks pronounced 

 their beautiful language. The frogs of the nineteenth century have 

 probably been faithful to the pronunciation of their race in former 

 times; and, as we listen in the still night to their curious music, it is 

 exactly as if one set of them, perhaps the tenors, the gentlemen of the 

 choir, kept singing "Brekekekex," while the softer wooing of the ladies 

 is uttered always as "Koax, koax, koax." 



Coming on land meant a diversity of habits, for the 

 amphibian is primitively an aquatic animal. The Amphibia do 

 not lay a very large number of eggs ; but they lay them always 

 in the water. The spermatozoa are poured out over them and 

 are not introduced into the body of the female. The same is 

 true of lobsters and cray-fish and certain other Crustacea. 

 The next two groups of Vertebrata, the Reptilia and the Aves, 

 produce comparatively few eggs and they are fertilized inside 

 the body of the mother. They are large and provided with 

 a great amount of yolk to serve as food for the embryo. They 

 are often protected by being buried in the sand, or otherwise 

 tucked away in skilfully constructed nests. 



It is in the mammalia that the embryo develops within the 

 body of the mother. Here the egg is fertilized and the number 

 of the spermatozoa which pass into the motlier's body is 

 incredible. In some species there are estimated to be some 

 226 miUions of spermatozoa; at other times 551 millions 



