592 SCIENTIFIC RECOKD FOR 1884. 



the young thau would be possible did this depend on the sluggish Acti- 

 nophrys form." {Proc. Acad. Nat. Sei., PJiila., 1884, pp. 17-19.) 



Infusorians. 



A ma></inal membrane in Trichomonas. — A hitherto unobserved pecu- 

 liarity of Trichomonas has been observed, which should incite to a re- 

 examination of related forms. At the anterior end of Trichomonas 

 rof/iiialis as well as T. hatrachcrum, al)oiit the base of the three liagella, 

 T. Blachmaiin discovered an "•uiiduhiting membrane" which "extends to 

 about the middle of the body ; this membrane, never hitherto observed, 

 may be best seen if the creature is allowed to die gradually." 



It is also recorded of Trichomonas hatrachorum and Trichomastixlacertce 

 at least, that "if the monad is allowed to remain for some time under the 

 l)ressure of the sun-glass the^whole margin of the animal is seen to ex- 

 hibit an active undulatory movement, though of course this is not so 

 regular as that of the membrane." {Zeitschr. f. iciss. Zool, XL, pp. 42- 

 49; J. B. M. S. (2), iv, p. 759.) 



PORIFEES. 



Sponges. 



Fossil sponges. — Although many fossil sponges have been described, 

 the infojraation regarding them has been very scattered and altogether 

 in an unsatisfactory condition. To a large extent this defect has been 

 remedied by the publication of a "Catalogue of the Fossil Sponges iu 

 the Geological Department of the British Museum, with descriptions of 

 new and little-known species," by Dr. George J. Hinde. No less than 

 14L genera were represented by specimens in the Museum ; of these 120 

 contained siliceous sponges, and the rest calcareous. Of the species, 

 32 belonged to the Palaeozoic times, 10 to the Triassic, 96 to the Jurassic, 

 245 to the Cretaceous, and only 3 were of Tertiary origin. The species 

 have been illustrated by 38 plates. 



Some modifications of sponge spicules. — A notable modification of char- 

 acter induced in fresh-water sponges has been encountered by Mr. 

 Edward Potts. This modification has " apparently been aliected by the 

 peculiar condition of the environment.''' Amongst the sponges which 

 Mr. Potts found "encrusting certain old pipes, recently removed, from 

 the water-works in the Schuylkill river in Philadelphia," some portions 

 of the one called Meyenia Leidyi were "much more deeply colored with 

 rust than others, the statoblasts, particularly, seeming to be mere pseu- 

 domorphs of their originals in iron oxide. Fragments of this character 

 were boiled in nitric acid, washed out and mounted for comparison with 

 other matter simihirly treated, b it free from such discoloration." "The 

 normal skeleton spicule of the Meyenia Leidyi is "smooth, robust and 

 shorter than that of any other .American species. Very rarely the fitie 

 line of the axial channel is visible, but in the specimen under exaiuiu- 



