June 11, 1897.] 



SCIENCE. 



921 



To me this is a far more important single 

 concept than any other to explain co-ordination 

 of all kinds, even the continuance of the healthy 

 life of cells in higher animals, unless it be that 

 of the influence of protoplasm on protoplasm, 

 per se, and directly. Nevertheless, this doc- 

 trine of the influence of one cell on another, 

 through chemical agency, which the theory 

 of the constant effect of the nervous system 

 renders clearer for all higher animals, Is one 

 that is also indispensable and which we are now 

 beginning to understand in more detail. The 

 main purpose of this communication is to put 

 forward as broad a basis as possible for concep- 

 tions of the nature of living things, for the 

 exact demonstration of which in a way to sat- 

 isfy a rigid logic we must still wait, it may be 

 long, but which we cannot aflbrd, in the mean- 

 time, to ignore without making many errors and 

 unduly restricting the field of view. 



Wesley Mills. 



McGiLL Univeesity, 

 Montreal, May 13, 1897. 



HIGHHOLE COUBTSHIP. 



Some mornings since I observed two highholes 

 on the same branch evidently in courtship. 

 The male, as I took it, would give a few clucks, 

 and rapidly bob its head up and down four or 

 five times describing about a quarter of a circle, 

 and the female then responded with the few 

 clucks and corresponding motions. This was 

 repeated at short intervals, and they flew to 

 another tree, and continued this rather comical 

 performance. Mr. Burroughs, in describing this 

 courtship of the highhole, speaks of the female 

 as 'unmoved,' which, however, was plainly not 

 so in this case. As the meaning of the head 

 bobbing I would suggest that the motion, being 

 much the same as when pecking at a tree or in 

 the turf, may signify the offering of food. The 

 male says, " Come with me and I will find you 

 lots of fat grubs," and the female assents by the 

 same acts and signifies mutuality. The whole 

 is in the same line of sentiment and action as 

 that of the young man who offers his best girl 

 ice cream and soda water. I may also mention 

 that I have often noticed this spring what I 

 supposed to be the male blue jay approach his 

 mate with a cluck and transfer to her bill some 

 article of food, the whole affair appearing to be 



gallantry. It may even be that the kiss is a 

 survival of lip-to-lip feeding. 



As to the pugnacity of birds in early spring I 

 may mention that some seasons since I observed 

 a cock robin fight for some hours his own reflec- 

 tion in a cellar window. This season a mirror 

 was placed upon a wren's box which had been 

 usurped by a pair of English sparrows. The 

 female fought her reflection most furiously, but 

 the male showed more intelligence, investigated 

 carefully, and would retire around the tree and 

 peer out to see if the supposed bird would move 

 toward the nest. At nightfall he took his place 

 before the mirror, as if on guard. A carefully 

 conducted series of experiments with mirrors 

 upon birds and other animals would, by provid- 

 ing the new environment, be of great value in 

 testing intelligence. 



Hiram M. Stanley. 



Lake Forest, III., May 5, 1897. 



a question op classification. 

 To THE Editor of Science : In your issue 

 of December 18, 1896, pp. 918-922, in a com- 

 munication by myself entitled ' A Question of 

 Classification,' through a typographical error I 

 am made to say that ' ' all other students place 

 the Dakota formation in the middle of our 

 American Upper Cretaceous." The word 

 ' Upper ' should have been omitted from this 

 sentence, as it was my intention to say that 

 ' ' all other students place the Dakota formation 

 in the middle of our American Cretaceous and 

 at the base only of the upper of the two great 

 series into which the Cretaceous of this country 

 is divided." 



KOBT. T. Hill. . 



SCIENTIFIC LITEBATUEE. 



The Materials of Construction. A Treatise for 



Engineers on the Strength of Engineering 



Materials. By J. B. Johnson, Professor of 



Civil Engineering in Washington University, 



St. Louis, Mo. New York, John Wiley & 



Sons. 1897. 8vo. Cloth. Pp. xv+787, 



with 9 plates. Price $6.00. 



This work is divided into four parts, the first 



treating of the mechanics of the subject, the 



second of general properties of materials, the 



third of methods of testing, and the fourth of 



results of tests. The number of pages in these 



