Dr Grant on the Structure and Nature ofFlustra. 109 



formed by the developement of bodies which are protruded from 

 the old cells contiguous to them ; and that, in the middle space, 

 between the margins of the branches, we find the old polypi, for 

 the most part, dead, or entirely removed from the cells. These 

 views regarding the nature of Flustrae, seemed to be confirmed 

 by the statement of Basterus, that the polypi have no connection 

 with the cells, and occasionally leave them entirely to seek for 

 nourishment ; and by the remarkable fact stated by Jussieu, 

 that, after having retained a living flustra for a few days in a 

 vessel of sea- water, he observed that all the polypi had left their 

 cells, and lay motionless at the bottom of the vessel. There 

 can be little doubt, from what I shall state hereafter, that this 

 appearance, observed by Jussieu, consisted of the escape of the 

 ova from their cells, and probably their fixing themselves on the 

 bottom of the vessel. I have found them often fix themselves 

 permanently on watch-glasses in less than six hours after their 

 escape from the cells. Basterus quotes Roesel as having like- 

 wise observed the polypi to swim to and fro after leaving the 

 cells, (Bast. Opusc. sub. p. 61., and Roesel. Supp. p. 605.) The 

 same sentiments are still entertained by the most distinguished 

 naturalists, both regarding the independent nature of the cells 

 of Flustrae, and their mode of formation by the successive de- 

 velopement of small vesicles or gemmules which have fallen from 

 the mouths of the old cells. Lamouroux states (Hist, des 

 Polyp, p. 99), that, when the polypus of a flustra has attain- 

 ed its full -size, it discharges through the opening of its cell 

 a small globular body which attaches itself near that aperture, 

 increases in bulk, and soon assumes the form of a new cell. 

 Lamai'ck maintains (torn. ii. p. 154.), that the polypi of these 

 animals have no communication with each other, no common 

 connecting substance, and " do not form compound animals ;**' 

 that the gemmutes, or reproductive vesicles, after detaching 

 themselves, fall into a determinate position beside the other 

 cells ; that each polypus probably perishes after producing a 

 single vesicle, and that the polypi are hence likely to be found 

 alive only near the outer margins of the branches. As the 

 branches of Flustrae almost always expand in breadth from their 

 basc'to their free extremity, by the successive interposition of 

 new rows of cells, which continually disturb the parallelism of 



