Miscellaneous. 491 



maxillary extending to below the front margin of the orbit. The 

 lower jaw projects beyond the upper. The teeth are villiform, those 

 of the palatine bones minute and forming only a short series. The 

 eye is of moderate size, one-fourth of the length of the head, and 

 much wider than the interorbital space. The scales advance supe- 

 riorly to between the hind margin of the orbits, and inferiorly to the 

 praeorbital. None of the bones of the head are serrated ; the prse- 

 operculum has two ridges along its margins, like Apogon, but the 

 ridges are very close together. The spinous dorsal fin commences 

 somewhat nearer to the snout than to the root of the caudal ; the 

 length of the first spine is not quite one-half of that of the second, 

 which is the strongest and longest, its length being one-half of that 

 of the head ; the following spines rapidly decrease in length. The 

 soft dorsal fin is slightly continuous with the spinous, both being 

 nearly equal in height ; its anterior spine is short, although longer 

 than the last of the spinous dorsal. Caudal fin rounded, its length 

 is contained six times and a half in the total. Anal spines strong, 

 the second and third are nearly equal in length. The root of the 

 ventrals is situated behind that of the pectorals ; they do not quite 

 extend to the vent, and are as long as the pectorals. The colour 

 a])pears to be greenish above, each scale having a darker margin. 



Two specimens of this fish, the larger of which is 33 lines long, 

 were received from the Murray River, and, having been given me 

 for determination by Mr. Holdsworth, are now deposited in the 

 British Museum Collection. — Proc. Zool. Soc. March 26, 1861. 



On the Retrograde Metamorphosis of certain Nematode Worms. 

 By Dr. R. MoLiN. 



In the females of four species of the genus Hystrichis, M. Molin 

 describes a phenometion which he considers as a kind of retrograde 

 metamorphosis — a phenomenon which puts a period to their exist- 

 ence, and which is in relation to the development of the generative 

 organs. The adult and fertilized females constantly hollow out a 

 gallery in the coats of the oesophagus of an aquatic bird. Imme- 

 diately afterwards there commences in them an extraordinary deve- 

 lopment of the generative organs. These organs attain such large 

 proportions that the skin of the worm is distended by them, and the 

 animal becomes gradually converted into a sort of vesicle. M. Molin 

 admits that this metamorphosis brings on the destruction of the body 

 of the mother, and that the ovaries with the eggs are thus set free. 

 Lastly, the embryos, on becoming developed, quit the gallery or 

 cyst, which is cicatrized. From the drawings and descriptions of 

 M. Molin, the worm, when distended, appears to retain its intestinal 

 canal. It would seem therefore that there i3 simply a dilatation of 

 the body of the mother without any true retrograde metamorphosis, 

 unless it be that there is a kind of degeneration of the skin. The 

 fact itself, however, does not thus lose its interest. — Sifzungsber, 

 der Akad. der Wiss. zu Wien, xxxviii. p. 706 ; Bibl. Univ. Ay^yW 

 20, \S&\,Bull. Scient. p. 388. 



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