( 534 ) 
In brackets after the figures of both series is given the place 
number which each of the genera would take in a regular classifi¬ 
cation. A comparison of these place numbers shows at a glance in 
how far the position and the slope of the For. magn. go hand in 
hand. In general there appears to be a decided parallelism between 
these features in monkeys, and only in a few cases there is a fairly 
marked difference between position and slope. This is, for instance, 
the case in Chrysothrix where the angle is small in comparison to 
the position, and in Colobus where the reverse is the case. 
: ,^ t L the be g innin g of this paper mention was made of the opinion 
held by Huxley, viz. that the slope of the For. magn. is in proportion 
to the degree of prognathism. In a following communication, which 
will deal with the prognathism of the primate skull, this view will 
be discussed at greater length. 
Physics. — “A short reply to Mr. van Laar’s remarks .” By Prof. 
Ph. Kohnstamm. (Communicated by Prof. J. D. van der Waals). 
In the proceedings of the preceding meeting of this Academy Mr. 
van Laar made some remarks suggested by a paper by Mr. Timmer¬ 
mans and me. Though these remarks do not call in question in any 
point the validity of our results, but exclusively deal with the 
question whether we have done sufficient justice to the share Mr. 
van Laar has had in the construction of the theory, 1 think that 
both politeness to Mr. van Laar and deference to the communicator 
of these remarks forbid me to leave them unanswered. So I shall 
y to state as shortly as possible the reasons why I still think I 
have done foil justice to that share. 
1. Mr van Laar writes in point a of his remarks: 1 ) “Here I must 
remark that I have neve's*) represented the special case ^ — j/a, a, 
as the general case/’ 
In writing this Mr. van Laar had certainly forgotten that he 
wrote m These Proc. Sept. 1906 p. 227: “In the third paper in 
These Proceedings (June 24, 1905) the equation: 
for the quite general ’) case a,: 
(3) 
was derived. 
And on t be same Page: “Now the restricting supposition 0 = 0 
0 These Proc. XII p. 455. 
*) Mr. van Laar’s italics. 
