Dr Grant on the existence and itses of Cilice, S^^c. 121 



impurities, rather than as essential parts of the mixture. In 

 this view the oxahverite would be a variety of apophyllite. 



Art. XXV. — On the existence and uses of Cilice in the 

 young Gf the Gasteropodous Mollusca, and on the causes of the 

 spiral turn of Univalve Shells.* By R. E. Grant, M. D. 

 F. R. S. E. Fellow of the Royal College of Physicians of 

 Edinburgh, and formerly Lecturer on Comparative Ana- 

 tomy. Communicated by the Author. 



vVhen we examine the surface of the minutest animalcules witli 

 a powerful microscope, we perceive that their quick locomotions 

 are produced by the rapid vibration of very minute processes 

 termed cilice, variously disposed on the surface of the body in 

 the different species. In zoophytes, whose fixed and inert 

 axis prevents them from swimming to and fro in search of 

 prey like animalcules, we observe incessant currents of water 

 directed to the mouths of the polypi, caused, not as is gene- 

 rally supposed by the motions of the tentacula, but by the quick 

 vibration of cilice disposed either on the tentacula, or around 

 the mouths of the polypi. I have already shown that the 

 same minute vibratory organs exist on the surface of the re- 

 productive gemmule&, or so named ova, of a great variety of 

 zoophytes, enabling these fixed and apparently inert animals 

 to rise from the bottom of the sea, and swim rapidly from 

 place to place during the first stage of their existence, sepa- 

 rate from the body of the parent. Although the cilicB, in the 

 simplest orders of animals, might be considered as organs of 

 motion destined to supply the place of the muscular svstem, 

 a more extended application of the microscope will show that 

 ihey are not confined to animals thus low in the scale, but are 

 likewise of frequent occurrence in such as have the muscular 

 and nervous systems highly developed, and probably that 

 •they have some influence in the first developement of the em- 

 bryo of the most perfect animals. While watching the pro- 

 egress of the embryo of the Buccinum undatum, and of the 



* Read before the Wernerian Natural History Society of Edinburgh 

 on the 24th March 1827. 



