214 Agassiz's Contributions to the 
Tarp. The frequent synthetic character of the earlier types. The 
Ganoid fishes are a familiar illustration, being often called Sau- 
roid fishes, as they include certain reptilian characteristics in 
their structure. They are synthetic types. T'o the Ganoids (and 
in other cases when a future group is foreshadowed), the term 
prophetic type is applied by Agassiz. In after time, fishes come 
out purely fishes in the Ctenoids and Cycloids, and this is, in 
_ part, the kind of expansion or evolution the Fish type under- 
went. The arborescent Acrogens of the Coal Period appear also 
to have been synthetic types, combining certain Coniferous char- 
acteristics with those of the Fern type. In this case the two 
wider range in their characters; as time moved on, the same 
a manner to favor the notion of the creation of ppt from an 
etween gro 
A FoURTH law is that of the culmination and disappearance of 
n the 
examples. This is obviously parallel with the fact in embry". 
logical development, that parts may fulfil their end and disapp® 
_* This subject is illustrated in its geological bearings at some length in Carpe? 
ter’s Comparative Physiology, 4th edition. . — ° 
«. 
4. 
