Wyman] 440 [April 15. 



■with any pnblislicd species, and the Rhizosolenife wove all too much 

 broken to afford specific characters. 



Mclosira graniilata is said by all the authorities to be afresh water 

 fona, but the specimens have all the characters of that species. 



It Avould be an unwarranted conclusion that these organisms were 

 obtained from their native locality. From their minute size they 

 may have been brought by currents or winds, or in the intestines of 

 fish or birds from far distant places. 



The Melosira sulcata is the only one sufficiently abundant to indi- 

 cate that it was found in its native habitat. 



April 15, 1868. 



The President in the chaii-. Thirty-five members i:»resent. 

 Tlie following paper was read : — 



Observations on Crania. By Jeffries Wyman, M.D. 



1. Measurement of Skulls. 



Tiedemann appears to have been the first, to attempt anything like 

 an extensive comparison of human crania based upon their capacity.* 

 To this end, 1, he weighed the skull without the lower jaw ; 2, 

 filled the skull with dried millet seed and weighed again; 3, deduct- 

 ing liie weight of the skull he obtained the weight of the millet seed 

 filling it. Thus a means for determining the comparative size of 

 the cranial cavity in different individuals or races was obtained, but it 

 failed to give any exact idea of the volume of the brain. The 

 method proposed by Sir William Hamilton was moi-e successful; he 

 filled the cranium with fine sand, which was measured in cubic 

 inches; having determined the weight of a cubic inch of sand, he 

 nuiltiijlied this by the number of cubic inches contained in tiie skull, 

 and making a correction for the difference in the specific gravities of 

 brain and sand, the weight of the brain was approximately reached. •, 

 Prof. Daniel Treadwell has proposed a somewhat similar, but more 

 simjiie method than this; it consists in determining, by any given 

 method, the capacity of the skull in cubic inches, multiplying this by 

 the weight of a cubic inch of water, and correcting for the difference 

 between the specific gravities of brain and water, we have, as in the 



* Phiios. Trans, of the Koyai Society of London, 183G, p. 497. 



t Lects. on Metaphysics and Logic. Edinburgh, 1860. Vol. i.; p. 240. 



