106 _ THE AMERICAN MONTHLY [June, 
sor Abbe fully concurs in this view. ‘The fineness of the longitudinal lines, 
their peculiar undulating character, and their direction parallel with the 
raphe, seem to preclude any possible error in this regard, as Dr. Van Heurck 
has already pointed out. 
6. Nobert’s 18th and 19th bands. This photograph was made with the 3 
mm. Zeiss lens and the 25 mm. ocular. The illumination was monochromatic , 
sunlight with a Powell & Lealand oil-condenser. 
As Dr. Pigott has so well said, there is no trace of diffraction lines about 
these photographs, and the lines stand out clear and perfectly sharp. Dr. 
Pigott * says, regarding diffraction spectra, that ‘ after all, these diffractions 
are not real and inherently uncontrollable. Nor do they require any elab- 
orate theory to account for what now have, fortunately, here ceased to exist 
in these splendid pictures due to the elaborate perfections of the compen- 
sations.’ 
Key to the Rotifera.— Continued. 
8. CEcISTES. 
a. Tube short or none ; foot thrice the body length . . . serpentinus. 
a. Tube short or none; foot not eens body length .. = welaczes: 
6. Tube floccose, irregular; body length “A, inch ... . . longicornts. 
6. Tube floccose, irregular ; body length = Pinch. \. <a! | on eegaBeleee 
6. Tube floccose, irregular; body length 4, inch . . . crystallinus. 
c. Tube gelatinous ; corona rveclobed we a ee Beare Remora 
c. Tube gelatinous; corona circular’) °°.) . +. 9. °. | . Oeapeeee 
@. Tube’ of pellets; antenne long" 1s.) 9: 2) 8 axe ee pilula. 
e. Tube membranous ©; «© . %) 0. 9) be 6 a 2 pace 
g. LACINULARIA soczalis. 
10. MEGALOTROCHA alboflavicans. 
11. TROCHOSPHERA @guatorialis. Marine. 
12. CoNOcHILUS. 
a. Tubes coherent, gelatinous; individuals many . . . . . volvox. 
a. Tubes distinct; colony 1 adult and few young . . . . dossuarius. 
13. PHILODINA. 
a. Body colorless; corona very wide, sulcus small . . megalotrocha. 
a. Body colorless ; corona ample, sulcus broad, shallow, erythrophthalma. 
6. Body dark brown, beset with spines . . PMN 514252. 
&. Body dark brown, beset with rough tubercles hee tuberculata. 
c. Body yellow, Tee constricted, foot slender . . . wl OCC E ga 
d. Body ruddy, translucent, not constricted ; foot stout. . . roseola. 
14. ROTIFER. 
a. Body white, smooth, tapering to the foot . . . « « | vbleahes: 
a. Body white, ends hyaline, suddenly attenuate to the long foot, macrurus. 
6. Body dull conn viscous, strongly plicate . . . 6h Se tgedarss 
6. Body clear brown, not viscous, not strongly plicate . HU Rapieegss 
c. Body hyaline, with longitudinalsteldss © 1-7): tear MACrOCeros. 
15. ACTINURUS zeptuntus:. 
16. CALLIDINA. 
a. Frontal column with 2 curved hooks . . . . . . . £6dzhamata. 
a. Frontal column without hooks (6). 
* English Mechanic. 
