2G4 DESCRIPTION OF {Polygastrica. 



bell increases in breadth ; a separation then commences, 

 and double circles of cilii are formed ; the body of the 

 animal then divides, and other cilii grow around the dome 

 of the bell ; by constantly whirling, one or both of the 

 bells separate from the stem, and swim about, in which 

 condition they have been classed as a distinct genus, under 

 the name Urceolaria. Should it happen that both the 

 bells are twisted off, the stem remains stationary, and 

 does not contract afterwards, or produce a new bell. The 

 most striking peculiarity which presents itself next is, that 

 the end formerly attached to the stem swims foremost, 

 and from the other extremity proceeds the new stem ; 

 before, however, this is effected, it changes its form, and 

 sometimes buds out, or separates ; the latter is the genus 

 Eclissa of Schrank, and the former, with the small protu- 

 berance, Rinella of Bory St. Vincent. If the creature 

 retain its bell shape, be not inverted, and exhibits the lower 

 cilii, it forms the genus Kerobalina of the latter naturalist, 

 and when all the cilii are invisible, then he calls it the 

 genus Craterina. Again, it constitutes the genus Urceo- 

 laria when the anterior cilii are alone observed. Besides 

 those already mentioned, there are many other changes in 

 its form ; sometimes it stretches itself out in length, and 

 becomes cylindrical, so that it is readily mistaken for a 

 species of the genus Enchelys; in this condition, one 

 or both ends bend themselves, while it is swimming 

 past a hard body ; finally it separates transversely in 

 twain. 



" The next method of propagation is by the bud forma- 

 tion, which is not confined either to the animalcules with 

 or without a stem. During this process, it passes through 



