754 



RKPOKT — -1892. 



The following explanation is ofi'ered : — The nuclear segreents being the organs 

 for the elaboration of food and the nucleolus a storehouse for elaborated material, 

 we must suppose that the new material which is being conveyed to the nucleus 

 will take on a blue stain, because during senescence, division, and other conditions, 

 when the cell may be supposed to be less actively assimilating food materials from 

 without, we have invariably a red colouration taken on by the chromatin. This 

 would also explain why the spermatozoon, owing to its great activitj', is not able 

 to lay up a store of elaborated material, and why it should stain blue, and why the 

 nuclei of fungi living on elaborated material should stain red. 



The view taken of the stainable material led of necessity to the belief that the 

 achromatin of the cell is the essential plasma, and the latter really seems to play 

 the most evident and important part during all phenomena connected with either 

 division or conjugation. 



Two special seats or centres of the achromatic substance may be recognised, one 

 being the archoplasma, the other the endo-nucleolar substance. From the central 

 endo-nucleolus, within the nucleolus, many delicate fibrils may be traced to the 

 hyaloplasm of the cell, and tubular fibrils may be seen to pass from the chromatin 

 segments to the nucleolus. 



These observations made by the autlior on the nuclei of Scilla nutans, after 

 fixing the ovules by his picro-corrosive alcohol, have been confirmed by M. Ileideu- 

 bain in his elaborate paper on the leucocytes of Salamandra inaculata. 



Department of Zoology. 

 1. On the Social Habits of S;piders. By Dr. McCooK. 



2. On a Use of the External Ear. 

 By Professor A. Crum Brown, F.B.S. 



The form of the external ear is such that a continuous uniform noise is heard 

 differently, both as to intensity and as to quality, when it strikes the ear at 

 different inclinations. As binaural hearing enables us to determine the azimuth in 

 which a source of sound is situated by turning round about a vertical axis until 

 the sound is heard equally in both ears, so the form of the external ear enables us 

 to find the altitude of the source of sound by rotating the head about a horizontal 

 right and left axis until we bear the sound with a quality and intensity which we 

 recognise as that of a sound proceeding from a source situated in the plane con- 

 taining the lines of direct visioii when these are in their mean position in reference 

 to the head. 



3. The Method of Comparative Psychology. 

 By Professor C. Lloyd Morgan. 



The object of this communication is to show that our interpretation of animal 

 inteDigence is necessarily based on a double or twofold process of observation. 



