1883.] 



MICROSCOPICAL JOURNAL. 



7Z 



"feathering" of an oar, while other 

 observers have seen in the same ani- 

 mal, an entire row of cilia suddenly 

 turn themselves as though by a shock, 

 and proceed to strike permanently 

 and rapidly in the opposite direction, 

 frequently returning as suddenly after 

 a time to the old direction. This has 

 never been observed in vertebrates. 

 According to Krause (1841) and En- 

 gelmann (1867) the number of oscil- 

 lations in a minute ranges from 180 

 to 620. Valentin * gives the follow- 

 ing table as the result of some fifteen 

 observations : 



ciliary motion have been observed 

 and classed as follows: (i) Hook- 

 shaped, in which the cilium during 

 the forward movement is bent for- 

 ward like a strongly flexed finger. 

 This would seem to indicate that the 

 cilia are strongly contractile through- 

 out their whole length. (2) Undu- 

 lating or flagelliform type of move- 

 ment, especially well shown in the 

 long cilia already referred to in Trich- 

 onyvipha agilis, Leidy, and also in the 

 spermatozoids of the frog, the undu- 

 lations proceeding from the base to 

 the tip of the cilium, (3) The vacil- 



The oscillations of all the cilia upon 

 the same cell are isochronous. Their 

 frequency is, however, to a high de- 

 gree dependent upon outside con- 

 ditions (temperature, moisture, etc.). 



The amplitude of the oscillations 

 likewise varies very much with the 

 variety of the cell and the external 

 conditions, but it is always alike at 

 the same time for all the cilia situated 

 upon the same cell. In ciliated 

 epithelium the amplitude usually 

 amounts to from 20° to 50° but at 

 times exceeds 90°. During the oscil- 

 lations the cilia, especially the short 

 varieties in ciliated epithelia, remain 

 unchanged as to form, either stiff and 

 straight, or slightly concave towards 

 the front (mollusca). Besides that 

 already described, four varieties of 



•PurKinje and Valentin, "Physiologic." 



lating motion, in which the movement 

 becomes pendulous, the to and fro 

 strokes being equal ; the plane of 

 oscillation however, being very chang- 

 able. 'I'his form has been observed 

 most frequently in spermatozoa, and 

 the lower organisms, but also in mol- 

 luscas. (4) Funnel-shaped move- 

 ment. This form is the exception in 

 all true ciliated epithelia, and contrary 

 lo the rule in all kinds of fiagellate 

 cells.* It is, however, seen, accord- 

 ing to Sharpey, in the slowing stages 

 and is characterized by the point of 

 the cilium defining a conic section 

 and the cilium itself the surface of a 

 cone. While the movements of all 

 the cilia belonging to the same epithe- 



* It has been noticed by Hofmeister in 

 in plants (zoospore, etc.,) and by others in the 

 spermatozoids of the canary, etc. 



