,1901) MICROSCOPICAL JOURNAL. 125 
Niteschia sigmatella Grun. Moller’s balsam type slide. 
Transverse stria extremely faint and difficult. A delicate 
object even with N.A. 1:3 and 1°4. 
Nitzeschia linearis and N. obtusa Sm. In balsam. The 
former very faintly resolved into transverse strix,the lat- 
ter not so difficult. Dr. H. Van Heurck, in his “Synop- 
sis des Diatomees,” gives NV. linearis as having 27 to 30 
striz in 0°01 mm, (25.399 mm.= 1 inch), and WV. obtuse 26 
to 27 in 0°01 mm. WN. sigmatella Grun., is given at 25 to 26 
strie in 0:01 mm., but the specimen of this form on the 
type slide has much finer structure than JN. linearis and 
NV. obtusa. 
Nitzschia sigmoidea Sm. Moller’s dry “‘Probe-platte”— 
253 to 26 strie in 0°01 mm. according to Van Heurck. 
This is remarkably easy with the 4 mm., the striz pre- 
senting a beaded appearance. They can be certainly seen 
with the 12 mm. apochromat of N.A. -65, so do not prob- 
ably, in this instance, exceed 55,000 to theinch. A speci- 
men in balsam is also very easy with the 4 mm. 
Nitzschia sigmaSm. Van Heurck gives 22 stria in 0.01 
mm. Distinctly dotted in balsam, and very easy in mix- 
ed monobromide of naphthaline and balsam. 
Grammatophora oceanica Ehrenburg. = G@. subtilissima. 
Moller’s dry “Probe-platte.”’ Resolved into transverse 
strie. Van Heurck gives 30 strie in 1:01 mm. forthe @. 
oceanica var. indica Grun., and 30 to 31 for the G. ocean- 
ica var. novaezeelandiae Grun. Some specimens of G@. sub- 
tilissima, however, are finer, running at about 88,000 to 
the inch. 
Navicula crassinervis. Striw 34 to 35 in 0:01 mm. ae 
cording to Van Heurck. This has proved-a most delicate 
object with the 4 mm., both dry and in realgar. With N. 
A. 13 and 1:4 realgar mounted valves are sharply resolv- 
ed into dots, but the transverse striw have alone been seen 
with the dry lens. 
' Hyalodiscus subtilis. In a mixture of monobromide of 
