60 NOTES. 
the voyage of the Hassler to make the collection of Selachians a 
principal object. He had been richly rewarded for his efforts. 
Since his return he had made careful examination of the collec- 
tion, comprising sometimes two hundred specimens of one species. 
The result of this examination was that while in their adult condi- 
tion the Selachians present characters which are very constant 
among specimens of the same age, there are such changes among 
them that even genera have been founded on the difference of 
age. Professor Agassiz then illustrated from abundant specimens 
and upon the blackboard the variations of dentition in Selachians 
of different ages from the embryo to the adult. In concluding he 
alluded to the relation which the facts of variation he had pre- 
sented might falsely be supposed to sustain to the development 
theory. The conditions which occupied a certain place in the series 
to be derived one from another should be consecutive in time. This 
was not the case. It was the endless series of anachronisms which 
were being made by the supporters of the transmutation doctrine 
which had kept him aloof from all such interpretations of Nature. 
When it should appear that these different features fall in time as 
they may appear to fall in their connection by similarity, then 
there would be some ground for the inference of a gradual change. 
Geologists ought to be as careful in their generalization as were 
physicists. He thought that there was too much loose twaddle and 
argument and debating-club demonstration in our Natural History. 
He had been told recently by one who occupies a very high posi- 
tion in science that “ unless you deduce one being from another 
you are not following a legitimate scientific course.” It should 
first be proved geologically that there is such a genealogical con- 
~ nection. The facts show, indeed, something that should not be 
overlooked, viz.: that there is thought in nature, and until it is 
proved that thoughts are derived one from another, he would not 
admit that the similarity of two objects proves their derivation 
one from the other. 
_ Mr. Alexander Agassiz made a communication on the “ Develop- 
ment of the Actiniz.” 
The second day’s session opened with an account of the glacial 
phenomena of the southern hemisphere compared with those of 
the north, by Prof. Agassiz. Any one who had been familiar with 
the glacial phenomena as exhibited in the northern hemisphere, 
th in Europe and the United States, and who would have ac- 
Sapa ees 
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