34. GEORGE BIDDER. 
bulk with borax carmine, and alone was cut by the ribbon 
method, all the other sections being made with the oblique 
razor. 
The distal expansion and fusion of the collars known as 
Sollas’s membrane (fig. 18) appeared plentifully in the paraffin 
sections of A, B, C, and F; scarcely at allin Dand E. It was 
not present in the living sections examined from any of the 
sponges; all alike showing the characters described in the 
previous paper. 
It was found that the average cubical contraction of the 
cells is about to one half of their living dimensions: 
Average volume of living collar-cell . . 270 cubic p. 
S5 » Of collar-cell in balsam = 25 
3 
This was calculated from the linear measurements, which 
contract unequally in different directions : 
Height! from 28 living cells . , o AD 
a 86 balsam cells . : Se at ist 
Basal width from 34 living cells ; Gas? 
is », 203 balsam cells i . 5°6p. 
Collar width from 50 living cells : . 46p. 
* » 126 balsam cells : . ody. 
The best series of sections (D, drawn in fig. 15) and the 
worst series (A, drawn in figs. 17 and 18) show respectively 
the following ratios in their linear dimensions to those of life: 
in Series D. in Series A. 
Collar width ; : : 83 : "5 
Basal width 4 P ; ‘88 ‘ ‘ 
Height . 4 : j 8 : "5 
Height of collar. ; 10 , 1:0 
Deduced ratio of volume of cell to that 
in life 4 : "55 5 2 
Deduced mean linear eantrantion ratio . 82 ; 6 
1 **Collar-width ” is measured at the origin of the collar from the cell ; “basal 
width ”’ is the length of a row of cells divided by the number of cells in the 
row; “height” is the distance between two parallel lines at right angles to 
the axis of the cell, and tangential to its apical and basal surfaces respectively, 
Contraction is here measured by the ratio of the fiual to the original magni- 
tude, referred to briefly as the ‘‘ contraction ratio,” 
