VOL. XLIII.] PHILOSOPHICAL TRANSACTIONS. JQ 



from time to time single polypi, which go swimming about till they fix each on 

 some body or other; and from these there again arise new clusters, in the manner 

 as above. The branches, from which polypi have detached themselves, still re- 

 main fixed to the cluster, but they bear no more polypi ; and after all the polypi 

 of a cluster have thus detached themselves from it, the assemblage of the branches 

 still subsists, but is of no further use. 



Mr. T. knew of 4 other species of polypi, that all increase in the same manner 

 as those abovementioned ; that is, which split and divide themselves according to 

 their length. Those which come the nearest to the first, are somewhat more 

 slender, and the branches of their clusters are transparent ; yet do they appear, 

 when there is a number of them together, of a changeable violet-colour : the 

 clusters of these bear a good resemblance to a sprig or aigrette of spun glass. 

 When these last animals are completely formed, it is not so easy to see distinctly 

 in them the motion of their lips, as it is in the other species beforementioned ; yet 

 may it be observed in these also, while they are still opening, and completing their 

 formation: for at such times, this motion is but slow, whereas it becomes after- 

 wards very quick in those that are entirely perfected. 



The polypi of the other species that he has observed, are yet less than the last: 

 they are shorter, but more open and hollowed at their anterior ends. These have 

 a character that sufficiently distinguishes them from all the other species: their 

 stems and branches have a motion that is not to be found in those of the other 

 polypi. These stems draw themselves up, and shorten all at once, taking the 

 form of a spiral wire or screw; and a moment after they again resume their for- 

 mer shape, stretching themselves out straight as before. These several species 

 of polypi, all multiply in vast abundance; but they have also enemies that destroy 

 immense numbers of them, and that in a very little time. 



Mr. T. also observed regularly other small polypi, of a different sort from those 

 that are found in clusters. These are nearly in shape like a tunnel, pretty long 

 in proportion to the opening of their larger ends. For this reason, Mr. De 

 Reaumur has thought proper to distinguish them by the name of tunnel-like 

 polypi. He is acquainted with 3 species of these last polypi, which are re- 

 spectively, green, blue, and white. Their anterior end particularly, is of a far 

 more compounded shape, than may at first be imagined. There may be observed 

 round the edges of this part, a sensible motion, much resembling that of an in- 

 dented wheel, or rather of an endless screw, turned very fast about. These 

 tunnel-like polypi form no clusters, like the others. The little bodies, that pass 

 swimming near the anterior parts of these insects, are in some manner drawn 

 into the mouths of their tunnels ; and sometimes a considerable number of very 

 small round animalcula fall one after another into these openings. Some of these 

 were indeed afterwards let out again, at another opening: but it could plainly he 



