The frequency of the classes e and f may merely be a way of stating that the scale of the telescope is too small to show the ordinary structure, but it must be remembered that many members of these classes are pretty large and bright and that the gradation in the series is apparently continuous. As far as telescopes of moderate focal length are concerned, the predominant form of nebulae as we know them at present is not the spiral, but is this same “e, f” class, described as round or nearly so, brightening more or less gradually toward the center, and devoid of detail. The brightest of the class are probably Messier 60 and N.G.C. 3379. Their spectrum, as derived from objective-prism plates, is continuous, and is probably of the same type as those of the spirals and the globular clusters. A detailed study on an adequate scale of the brighter members of the class will throw considerable light on the problem of the small nebulae. TABLE II ----------------------------------------- HUBBLE _minus_ STRASSBURG --------+----------------+--------------- N.G.C. | Δα | Δδ --------+----------------+--------------- 379 | 0ˢ.0 | + 3″ 380 | +0.1 | + 3 382 | +0.2 | + 1 383 | +0.1 | 0 384 | +0.1 | + 1 385 | +0.1 | + 2 386 | -0.2 | - 2 387 | +0.2 | + 3 3550[2] | +0.5 | +24 3552 | +0.1 | +19 3554 | -0.2 | +15 3558 | -0.3 | - 1 6329 | -0.3 | + 3 6332 | -0.3 | + 6 6336 | +0.1 | + 8 7586 | +0.2 | + 1 7608 | -0.3 | + 6 7611 | -0.2 | - 1 7612[3] | 0.0 | + 2 7617 | +0.1 | + 1 7619[4] | +0.1 | - 1 7623[5] | 0.0 | + 1 7626[6] | -0.2 | - 2 --------+----------------+--------------- [2] Nucleus is eccentric and undefined on the photograph, hence the photographic position is probably in error by several seconds of arc. [3] Mean of the positions given in Vols. III and IV. N.G.C. 7621 is 5ˢ.4 preceding, and 1′ 49″ south of 7623. There is a double star in the position published in the _Strassburg Annals_. [4] Mean of the positions given in Vols. III and IV. N.G.C. 7621 is 5ˢ.4 preceding, and 1′ 49″ south of 7623. There is a double star in the position published in the _Strassburg Annals_. [5] Mean of the positions given in Vols. III and IV. N.G.C. 7621 is 5ˢ.4 preceding, and 1′ 49″ south of 7623. There is a double star in the position published in the _Strassburg Annals_.