RECORDS. 181 



istics and reproductive ability or disability in Sainia cecropia. It 

 was shown that the pupae of those individuals, male and female, 

 which mated were different from those which failed to mate, 

 although all were placed under the same conditions as far as 

 possible. True reproductive selection was evident, and related 

 to typical conditions as well as to variabilities. A brief discus- 

 sion was given of the real basis for the selective process and of 

 the relation between reproductive selection manifested after 

 emergence to that selection which occurred during pupal exis- 

 tence. 



M. A. BiGELOW, 



Secretary. 



SECTION OF GEOLOGY AND MINERALOGY. 



April 20, 1903. 



Section met at 8.15 P. M., Professor James F. Kemp pre- 

 siding. The minutes of the last meeting of section were read 

 and approved. 



The following program was then offered : 



A. A. Julien, The Hornblende Schist of Spuyten Duvvil 

 Creek, Manhattan Island. 



D. W. Johnson, The Geology of the Cerillos Hills 

 New Mexico. 



Summary of Papers. 



Dr. A. A. Julien, in the first paper of the evening, presented 

 the results of his work on the hornblendic schist which occurs 

 at the extreme northern end of Manhattan Island, near Spuyten 

 Duyvil Creek. He was able in the first place to prove the un- 

 doubted igneous origin of this rock by the unaltered crystals 

 which it still preserves and which point to an original gabbro. 

 The speaker then presented his views in favor of the igneous 

 origin of all the hornblende schists of Manhattan Island. 



Mr. D. W. Johnson presented a paper on the " Geology 

 of the Cerrillos Hills, New Mexico." The Cerrillos Hills 

 form the most northerly group of a series of four laccolithic 

 mountain masses in northern central New Mexico. The rela- 



