376 Professor Floicer on WJiales, Past and Present, dc. [May 25, 



gradually become more and more piscivorous, as we know from the 

 structure of their bones and teeth, the purely terrestrial members 

 have become by degrees more exclusively graminivorous. 



One other consideration may remove some of the difficulties that 

 may arise in contemplating the transition of land mammals into 

 whales. The Gangetic Doljjhin (Plataniftta) and the somewhat re- 

 lated Inia of South America, which retain several rather generalised 

 mammalian characters, and are related to some of the earliest known 

 European Miocene dolphins, are both to the present day exclusively 

 fluviatile, being found in the rivers they inhabit almost up to their 

 very sources, more than a thousand miles from the sea. May this not 

 point to the freshwater origin of the whole group, and thus account 

 for their otherwise inexplicable absence from the Cretaceous seas ? 



We may conclude by 2:)icturing to ourselves some primitive gene- 

 ralised, marsh-haunting animals with scanty covering of hair like the 

 modern hippopotamus, but with broad, swimming tails and short 

 limbs, omnivorous in their mode of feeding, probably combining 

 water-plants with mussels, worms, and freshwater crustaceans, gradu- 

 ally becoming more and more adai)tcd to fill tlie void place ready for 

 them on the aquatic side of the borderland on which they dwelt, and 

 so by degrees being modified into dolphin-like creatures inhabiting 

 lakes and rivers, and ultimately finding their way into the ocean. 

 Here the disappearance of the huge Enaliosaurians, the Ichthyosauri 

 and Plesiosaiiri, which formerly played the part the Cetacea do now, 

 had left them ample scope. Favoured by various conditions of tem- 

 perature and climate, wealth of food su2)2)ly, almost complete immunity 

 from deadly enemies, and illimitable expanses in which to roam, they 

 have undergone the various modifications to which the Cetacean type 

 has now arrived, and gradually attained that colossal magnitude 

 which wo have seen was not always an attribute of the animals of this 

 group. 



Please to recollect, however, that this is a mere speculation, which 

 may or may not be confirmed by subsequent pala^ontological discovery. 

 Such speculations are, I trust, not without their use and interest, 

 especially when it is distinctly understood that they are offered only 

 as speculations and not as demonstrated facts. 



[W. H. F.] 



