REPETITION OF PAST HISTORY. 12$ 



parallelism is hopeless." It may be possible, he 

 thinks, to decide as to the general line along which 

 echinoderms have developed, but any attempt to 

 trace the history of genera in this way will only 

 result in complete failure. Embryology alone is not 

 a safe guide, and only so far as it is possible to verify 

 it by actual fossils, can it with justice be relied upon 

 as giving any thing more than a general history of 

 the past. The parallelism exists, but our power of 

 interpreting it is not great. This conclusion as to 

 limiting the use of embryology in teaching history, 

 has naturally been a disappointment to the enthusi- 

 astic embryologists, who have not hesitated to say 

 that the work of Agassiz marks a step backward. 

 But it is certainly a wholesome check to the too pre- 

 cipitous advance in this direction ; for the embryolo- 

 gist has begun to rank his science too highly, a 

 common fault with all specialists. But whatever be 

 the result obtained by Agassiz as to our power of 

 following this parallelism, there was no question on 

 his part that such a general parallelism does exist. 



Beyond this work of Agassiz, there has been rto 

 thorough attempt to investigate the matter. It 

 is so difficult to obtain a sufficient amount of fos- 

 sil material to make a satisfactory parallel, that 

 none have had the courage to attempt it. Of course, 

 from the fact that the assumption has been so con- 

 stantly in the minds of scientists, it has followed that 

 vast numbers of disjointed facts have been noticed 

 bearing on the point. Usually the investigator has 

 satisfied himself with observing a few isolated facts, 

 and saying that they form another instance of the 



