1915] 
Proceedings 
The desert. Here were seen the large tree-like cacti, and the acacia trees. 
Lizards the most typical animals of the desert. 
Mountain torrential streams; lowland rivers. Most all the animals in- 
habiting the torrential streams have developed accessory organs for guard- 
ing against dislodgment. The tree-frog carries its eggs on the surface of 
its back. Iguanas were seen near the lowland streams; mangrove swamps 
near the mouths of the estuaries. 
At the conclusion of a discussion of questions suggested by the lecture, 
Dr. Pearse was tendered a vote of thanks. 
The meeting then adjourned. 
Milwaukee, Wis., March 12, 1914. 
Meeting of the combined sections. 
Mr. Teller in the chair. Twenty-three persons present. Minutes of 
last meeting read and approved. 
Mr. H. Clowes, of the Public Museum, exhibited some new, life-size 
models of native Wisconsin plants. These models are to be installed in 
the Museum, as a part of the proposed synoptic exhibit in botany. The 
speaker then read a short paper on the preservation of plant material and 
on the preparation of specimens for exhibit. 
Mr. Teller described a number of the fossils of the Niagara formation at 
Racine. He illustrated his remarks by means of specimens. 
The meeting then adjourned. 
Milwaukee, Wis., March 26, 1914. 
Regular meeting of the society. 
President Barth in the chair. Twenty-five persons present. Minutes 
of last meeting read and approved. The name of Mr. Joseph D. Hood, 
Biological Survey, Washington, D. C., was presented for membership and 
referred to the board of directors for action. 
Word having been received from the treasurer, Mr. Beckmann, that he 
would leave the city permanently within a few days, it was voted that the 
secretary act as treasurer pro tern, until a formal letter of resignation would 
be given by Mr. Beckmann. 
The lecture for the evening was given by Prof. H. H. Newman, of the 
University of Chicago, on the subject “The Physical Basis of Sex Deter- 
mination. ” 
Professor Newman remarked on the inadequacy of the older theories 
and then gave the results of some of the latest researches into the question 
of sex in animals. 
There is a considerable body of soundly established facts to show that, 
the determination of sex depends on the “x” element in the sex cells. In 
all groups of animals, except birds and echinoderms, reduction, in the 
female, occurs in such a manner that there is an even number of chromo- 
somes in the egg cell; but in the male, there are formed two kinds of sex 
cells, one of which kind contains the unpaired “x” element or “x” chromo- 
