Mr. A. Hancock on Vermiform Fossils. 443 each other. But we have been unable to discover in these all the characters of an ovum with the same distinctness as in the preceding species, no doubt because they had not yet arrived at their complete development. V. I have not witnessed the deposition of the ova in these animals. It is very probable that they escape by the anus, or by some neighbouring aperture. Thus, in the Stylonychice, I have seen them collect in the posterior part of the body which bears the anal orifice, and diminish gradually in number from the first or second day after the copulation. It is a singular thing, that about this period a round pale body begins to make its appearance in the centre of the animal; this becomes con-stricted about the middle, and reconstitutes the double nucleus of Stylonychia. VI. The Infusoria are destitute of copulatory organs. In most cases the copulation is effected by simple juxtaposition, the two mouths establishing the sexual communication [Para-mecium, Bursaria, Euplotes, Chilodon, Spirostomum). In the Oxy trichina* the union is more intimate, and goes so far as to constitute a true soldering of the two individuals for more than two-thirds of their anterior part. Any one who had not wit-nessed all the phases of this singular copulation, would be unable to avoid regarding this state as a longitudinal division, proceeding from behind forwards, in a single animal. But even, if direct observation were wanting, the concomitant changes of the internal organs, which are so characteristic, cannot leave the least doubt as to the actual signification of this act. XLVIII. — Remarks on certain Vermiform Fossils found in the Mountain Limestone Districts of the North of England. By Albany Hancock*. [With six Plates.] In 1838, Mr. Dixon Dixon, of Unthank, presented to the Newcastle Museum a few slabs of a fine-grained micaceous sand-stone, which were procured from a quarry on Haltwhistle Com-mon. These slabs exhibited on their surfaces peculiar elevated and depressed markings, supposed at the time to be either the fossil remains of worms, or casts of worm-tracks. Slabs bearing similar markings were likewise obtained by Mr. Edward Wood, of Richmond, in 1850, from the same for-mation in Wensleydale, Yorkshire, and were described by that gentleman in two interesting communications published in the * Communicated by the Author, having been read at the Meeting of the British Association held at Leeds, September 22, 1858.
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