184 Dr. Barry's renewed Inquiries concerning the 



showed in their movements a shortening and lengthening. No 

 definite order, however, such as that impUed by undulation, was 

 observed. Perhaps a disturbance had occurred through mani- 

 pulation.] 



It is important, the author thinks, to have seen these undu- 

 latory movements performed by the cilia m, fig. 36 ; foi', as suc- 

 cessors to the cilia n, the cilia thus undulating were about to 

 arrange themselves in one of the two lines above mentioned as 

 combining to form a sort of tunnel, through which by their ex- 

 tremely vehement movements to drive a rapid current. And 

 the following occurred to him as possibly sufficient to explain 

 the appearance presented by these movements, — which have been 

 aptly compared to the rapid flow of globules of a fluid. The 

 cilia n, fig. 36, are all bent in the same direction ; they are 

 arranged in a line, and perform their swinging or lashing move- 

 ments in an undulatory manner according to the order of their 

 positions in that line. Like movements, and in the like order, 

 are performed by the cilia o in the opposite line ; their extremi- 

 ties alternating with the extremities of the cilia n in the first line, 

 like the fingers of the two hands, and moving without the slight- 

 est mutual interference. Now were the movements throughout 

 the whole phalanx of cilia contemporaneous, there would be pre- 

 sented to the eye a permanent line of swinging movements. As, 

 however, those swinging movements are performed by the cilia 

 one after another in the order of their positions in the line, they 

 assume the appearance of a row of roundish waves, following, or 

 as it were chasing, and uninterruptedly passing into one another ; 

 not rarely appealing to the eye like a long revolving screw. 

 The diff'ereuce between rows of globules (the appearance most 

 frequently presented by the movements in question) and screw- 

 cylinders, may be supposed to arise as follows : — When the 

 swinging movements are of difi'erent extent at difi'erent parts, we 

 have the appearance comparable to a row of globules; when 

 those movements pass uniformly into one another, there is seen 

 the long-revolving sci'cw*. 



Having found the cilia on the branchial laminse of Mussels to 

 consist of double spnals, the author deems it scarcely needful to 

 remark, that he infers a like structure in other cilia, exist where 

 they may. As, however, in the course of these researches he 

 has very often had the opportunity of examining cilia of Infu- 

 soi'ia, several species of which are met with in the fluid of the 

 Mussel's shell, he cannot refrain from making known the fact, 

 that in these cilia also he finds his double spiral. Often did he 



* [The screw probably exhibiting the normal, and the row of globules a 

 disturbed state.] 



