the transparent envelope, two contractile spaces, a nucleus and nucleolus, short gullet, mouth, depression on the central side leading thereto, and chlorophyll granules diffused through the fluid contents of the interior transverse fission has been observed, when the nucleus separates into two, each half being accompanied by its nucleolus. At the same time contractile cavities form themselves in each segment into which the body divides. I have observed frequent instances of true conjugation of Paramecia, twice in the month of January. They pair by placing themselves side by side. But I have occasionally seen two individuals swim about for a long time grappled end to end. and then come apart without actual conjugation. The cilia were unusually active at the point of junction. In Paramecium aurela two contractile vacuoles are seen, each branching out star-fashion into short canals, which appear distinct during the contraction of the central cavity, and are almost obliterated during dilatation, I have found this pretty species swarming in stagnant pools in spring.
Kerona, or Stylonychia, may he recognised by its slipper-like form, and the long spines and bristles with which it is furnished at both ends. In length it ranges from 1-275th to 1-100th of an inch. The body is also beset with smaller setæ, besides the active cilia by which it moves. A line of these organs leads to the mouth, which is fringed with them. The mouth itself is placed a little to one side, and is clearly indicated by the streams of floating particles which set towards the spot. In the rear of this opening is situated a contractile space, which dilates slowly but contracts suddenly, the whole movement taking about six seconds to complete. These animalcules have the queer halt of jerking hack at short intervals, as they make their way through the water. Sometimes two individuals will fasten on to each other by their terminal spines, and swim about so connected for a considerable time. The two species answering to the above description are K. mytilus and K. silurus. Another common species, K. polyporum, is bean-shaped, filled with numerous vacuoles, and armed with several hooks, but not with the long spines or bristles of the precoding. It is parasitic on other freshwater animals.
Euplotes charon belongs to a family of Infusoria which are characterised by the possession of a lorica. The body, in fact, is encased above in a boat-shaped horny shield, ornamented with lines of prominent dots. The organs of locomotion are very highly developed. Cilia, bristles, and hooks make the little creature quite formidable, and enable it to swim, crawl or climb, back upwards or downwards, with the greatest agility. A contractile vesicle and a nucleus are present. Euypletes may be looked for amongst Algæ and other water-plants at all seasons.
Amphileptus resembles, both in form and movements, a small leech, having a highly extensible proboscis, or prolonged upper lip. The other extremity tapers to a tail. Rows of cilia are disposed lengthwise ever the entire body; but these organs, as usual, are most conspicuous about the mouth. The interior is diversified by numerous food-vacuoles. One species, taken last June, seemed to me to be undergoing transverse self-division. I have generally found it amongst duck-weed.
