Clusters and Nebulae. 343 



observation, the parasites of the cockroach cannot but form a 

 most interesting study, as they not only present a great variety 

 of beings of a peculiar and specialized organization, but also are 

 very excellent initiatives to the study of the Entozoa generally, 

 of which there is yet so much to be ascertained and discovered 

 by the careful microscopic observer. 



Explanation of Plate. — Figs. 1, 2. Gregarina Blattse, 

 Siebold. Fig. 2 a. Yesicle, separated from the sac. Fig. 3. 

 Two individuals attached. Fig. 3a. Encysted Gregarina3. 

 Figs. 6, 7. Pseudo-naviculse of Earthworm. Figs. 8, 9. Young 

 Gregarinee of Earthworm. Fig. 10. Bodo Blattse (Vibriones). 

 Figs. 5, 6. Nyctotherus ovalis, Leidy : a, cc nucleus." Figs. 

 11,12. Ova of Anguillula macrura, Siebold. Fig. 13. Female 

 of Anguillula macrura : a, mouth ; b, c, dilatations of muscular 

 oesophagus ; d, intestine ; e, reproductive organs ; /, caudal 

 extremity. Fig. 14. Young individual. Fig. 15. Head and 

 muscular oesophagus; letters as before. Fig. 16. Gordius 

 orientalis, five times natural size. 



CLUSTERS AND NEBULAE.— DOUBLE STARS.— THE 

 PLANET MARS.— OOCULTATIONS. 



BY THE EEV. T. W. WEBB, A.M., P.E.A.S. 



Befoee the constellation Lyra sinks too far towards the horizon 

 we must take the opportunity of examining the most wonderful, 

 though not the most conspicuous, of the many telescopic 

 objects it contains. This will be 



24. The Annular Nebula in Lyra, 57 M. Between Wega 

 and /3 Gygni, but somewhat s of a line joining them, we notice 

 two 3 mag. stars, not far asunder. These are /3 and y Lyrce, 

 /3 being the nearer of the two to its great sovereign Wega. 

 Between them, about |rd of the distance from /5 to 7, we shall 

 detect, not probably with our finder, but by sweeping with a 

 low power, a minute disc of feeble light, with a darkness in 

 the centre, converting it into a ring. This singular object 

 was discovered by Darquier at Toulouse in 1 779, when a comet 

 happened to be passing near it ; but neither he nor Messier 

 and Mechain, the ancient observers of nebulee, perceived the 

 perforation, which was reserved for the eye of Herschel I. 

 That feature might probably be seen, nevertheless, very fairly 

 with 3 inches, or even a smaller aperture ; a power of 29 shews 

 it as a known object with 5i inches, but it rapidly gains in dis- 

 tinctness with increase of magnifying, which the whole nebula, 



