180 Dr. Barry's renewed Inquiries concerning the 



the author to consist oi fasciculi of cilia ; and if this be the case, 

 their mode of reproduction is probably the same as that of other 

 muscle. He found the bulb at the base of some cilia much 

 smaller than at that of others. This may have arisen from 

 di\isiou, — a larger bulb together with its cilium dividing into two ; 

 or it may have arisen from consumption of the bulb, through 

 nourishment and growth of the cilium. In other cases the bulb 

 had entirely disappeared, and the cilia arose from a common 

 giouud, fig. 35 h. Here it is possible that after the bulbs had 

 been entirely spent from the growth of the cilia, all trace thereof 

 had disappeared. 



Notwithstanding all that he has said, both in this treatise and 

 in former ones, on the necessity in all researches on the struc- 

 ture of tissues of attending to the history of their development, 

 the author adds that he feels called upon candidly to acknow- 

 ledge cilia to present in this respect a difficulty such as perhaps 

 is scarcely to be found elsewhere. Here the observer has it not 

 in his power to beffin with the history of development ; for after 

 what has been above stated of a continued renewal of the cilia, 

 and of several stages in their development being sometimes met 

 with even in the same bar, it cannot be expected that the younger 

 cilia will necessarily be found in the younger mussels. The few 

 facts in their development recorded in this memoir, were not 

 fully ascertained until after a long series of measurements and 

 observations on movements, and on forms of cilia met with quite 

 at random. The author trusts his descriptions and drawings of 

 the several stages may be useful to others in following out the 

 history of development ; b t it is a misfortune for him not to 

 have it in his power to say just where the younger and most 

 convincing stages are to be found, such as would enable others 

 so easily to confirm his observations on their spiral structure. 

 It is added : " You may open a very large number of mussels, 

 and devote whole days to the examination, before you find an 

 example for demonstration. If, however, you are so fortunate 

 as to meet with a stage such as that in fig. 30, you feel richly 

 rewarded for all the labour." 



The author then proceeds to establish his position No. 2, that 

 the cilia marked m in fig. 36, &c. are merely different stages in 

 development of the cilia n in the same figures. To this unex- 

 pected observation he was led by the follomng facts. 



In the first place, the cilia in and n, see fig. 36, have a common 

 place of origin, their roots ai-ising mixed together in the same 

 field. Secondly. You here and there see one of the cilia m flexed 

 at its base, by which its extremity is made to approach the ex- 



