ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
483 
area of the entire plate. The ratios are 2 : 1 = 9 ; 3 : 1 = 25 ; 4 : l§ji 49 ; 
5:1 = 81; 6 : 1 = 121 ; 7:1 = 169 ; 8:1= 225. 
Tims, if in a sector circle of circle G, the average number of colonies 
were 12, then the number of colonies is 12 x 121 = 1452. 
New Test-Plate.* — Dr. H. van Heurck, after alluding to the scarcity 
of Nobert’s plates, suggests that microscopists may avail themselves of 
the markings of diatoms for the purpose of testing the resolving power 
of lenses. The author has carefully worked out the following table, 
giving in parallel columns the diatom-equivalent of Nobert’s series. 
Nobert’s series stops at 19, but the author has continued the calcula- 
tion for 20, 21, and 22. 
Nobert’s 
Series. 
Number of 
Lines. 
Number of 
Diatom Lines. 
Corresponding Diatoms. 
1 
443 
445 
Navicula dactylus (str. trans.) 
2 
665 
620 
„ lyra „ 
3 
886 
900 
Epithemia turgida „ 
4 
1108 
1100 
Navicula Brebissonii „ 
5 
1329 
1330 
Stauroneis phoenicenteron (str. trans.) 
6 
1550 
1500 
Pieurosigma balticum „ 
7 
1572 
1800 
„ angulatum „ 
8 
1994 
2000 
Mastogloia meleagris „ 
9 
2215 
2200 
Surirella gemma „ 
10 
2437 
2400 
„ (str. long.) 
11 
2658 
2600 
Mastogloia exigua Lew. (str. trans.) 
12 
2880 
2800 
Van Heurckia rhomboides typ. (str. trans.) 
13 
3100 
3100 
Nitzschia linearis Sm. (str. trans.) 
14 
3323 
„ „ var. tenuis (str. trans.) 
15 
3544 
3400 
Frustulia saxonica (str. trans.) 
16 
3766 
3600 
„ (str. long.) 
(3800) 
17 
3987 
t0 
Amphipleura pellucida (str. trans.) 
(4000) 
18 
4209 
4200 
„ „ small (str. trans.) 
19 
4430 
20 
4652 
21 
4872 
22 
5093 
5000 
„ „ (str. long.) 
Improved Form of Wash-bottle.^ — Mr. W. C. Sturgis describes a 
wash-bottle devised by Mr. A. L. Winton. The apparatus is easily made, 
easily manipulated, and under perfect control. It consists of a glass 
* Zeitschr. f. angew. Mj^kr., iv. (1898) pp. 1-4. 
f Journ. Applied Microscopy, i. (1898) pp. 75-6 (1 fig.). 
