16 W.S. Sullivant and T. G.Wormley on Nobert’s Test Plate. 
Many frustules of these a spt from different localities, a : 
‘Ple 
been measured by us and always with the same resu 
not afew under 1; of an inch in length, were measured, and 
on no one were found striz less than 52 or more than 56 in 
001”, much the larger number being 54. A similarly uniform — 
striation has always been observed among the individuals of — 
us 
many other species examined b 
o such uniformity of striation Amphipleura pellucida forms q 
ong © 
as yet no exception; this diatom is still a “res vexata” am 
microscopists ; neither the striation nor the aeueiubs of its frus: 
tule is at all satisfactorily understood. The record of its stria- — 
tion is found to be thus :—in 1854 Messrs. Harrison and Sollitt’s 
measurements made its strize 120 to 130 in -001”;—Prof. Carpen- — 
ter Se akint — suggests the probability of some error in these | 
measurem —the writers of this paper declared themselves — 
(this oo, “March, 1859) unable to “glimpse” the striaze;—Mr. — 
gain and finds them 
Sollitt (Mic. Jour., Oct. 1859) measures them a 
° 
still as low as 120 to 130 in 001”, but gives it as the opinion — 
of Mr. Lobb that “even those figures are too low and that they — 
ought to be set down at 140 in O01": ;’—1in the same number 0 
the Microscopic Journal, Mr. Rylands sees “‘strize, but much more | 
distant than the 130 in “QOL of the Hull microscopists ”"—lastly 4 
Mr. Hendry states (Mic. Jour., July, 1860) that he has “come to — 
a satisfactory conclusion, that ‘* is a sad ictapsoteniicl to seb — 
down the lines so high in the scale as 180 in 001”, and that on — 
a few ae ne lines may be counted at 42, and many at 60, 70 and — 
80 in rplexing — truly |—reminding one ¢ 
the celebrated Tor a Hill coal case (Mic. Jour., ii, p. 
It is our impression, notwithstanding these radar Nt state- 
ments, that the diatom before us presented to all these gentlemen 
the same appearances, but their eee rictataas of these appear- — 
ances have been widely differen 
The testimony of our ace. as we understand it, seems ~ 
to indicate that this diatom has a minutely and irregularly bro- 
ken up surface, which even on nig from mi 2 can be nqde bas 
specimens from "Hall, sent us 7 Mr.G. Rowen 
failed, with glasses too of unsurpassed es to 
