NATURAL SCIENCES OF PHILADELPHIA. 19 



many changes which species have encountered through the course 

 of ages, the peculiar adaptation to special temperatures has been 

 among the least changeable of characters. Of course what are 

 known as theories of evolution hardly find a parallel in the cases 

 he had referred to. Evolution deals with the modification of 

 organs. It is still the same organ though changed in form. The 

 modified leaf is still a leaf, though it may be contended to be 

 specifically distinct from its parent. In the cases he brought for- 

 ward it was an absolute change of one organ to another organ. 



OCT ' 



Yet he thought it was impossible to conceive of evolutionary 

 movements wholly independent of morphological laws. However, 

 he offered the facts for whatever they might be worth, and the 

 suggestions on them only as leading to thought on the greater 

 question. 



On Green-Sand Vertebrate/. Prof. Cope made some observa- 

 tions on the vertebrates of the New Jersey' cretaceous, and de- 

 scribed the characteristics of several species of gavials. The genus 

 Hyposaurus possesses a sagittal crest. The H. fractercuhis, Cope, 

 is the smallest of the species, and must be referred to the genus 

 Gavtalis. The chimseroid fishes are very abundant, about twenty 

 species being included in a monograph of them now in course of 

 publication. They belong to the genera Leptomylus, Cope, Diph- 

 rissa, Cope (type Ischyodus solidulus), Ischyodus, Egvt., and 

 others. Leptomylus for/ex, and numerous other species were de- 

 scribed for the first time. 



Effects of Cold on Iron. Mr. Willard referred to two in- 

 stances of the brittleness of iron under the prevailing low tempe- 

 ratures which he noticed yesterday. In breaking up an old loco- 

 motive, the cutting off of the rivet heads, which usually requires 

 heav}' sledging, was effected by a single blow, as if they were 

 made of cast iron. In the forging of a long steamboat shaft of 

 the best hammered iron which hung balanced in a crane, the ham- 

 mering of the heated end caused vibration in the overhung end 

 harmless in ordinary temperatures, but at 10 P. sufficient to 

 cause the beam to break sharp near the point of support. The 

 published tests of iron and steel show no loss of tensile strength 

 at low temperatures under a gradual stress, but all experience 

 shows great loss of body, or ability to resist a blow. 



February 1G. 

 The President, Dr. Puschenberger, in the chair. 

 Twenty-eight members present. 



Mr. Henszey announced that Mr. Isaiah V. Williamson had 

 given to the Academy ground-rents to the amount of $25,000, the 



