VOh. XLIV.] PHILOSOPHICAL TRANSACTIONS. 389 



their figure, and become nearly oval. There are in a cluster but few of these 

 bulbs, in comparison of the great number of polypi that are on the same; nei- 

 ther do these bulbs all come out at the same time. 



It is now easy to judge of the remarkable difference there is between the 2 

 sorts of clustering polypi that are described in this paper. The clusters of the 

 first species of polypi, and those of several others which he had also observed, 

 do all come from polypi detached from the clusters already formed. But the 

 clusters of the polypi of the second species here described, do not arise from 

 polypi detached from other clusters, but from round bodies or bulbs, larger than 

 those polypi, and of a form very different from them. These bulbous bodies are 

 not formed like the polypi, by the division of others like themselves, but they 

 spring from the branches of the cluster, as the flowers and the fhiits of a tree 

 spring from the branches of the same. 



In divers other species of polypi, there are considerable intervals of time be- 

 tween their divisions. In the bulbous kind, if they may be called so, the first 

 divisions are consecutive, and follow hard on each other, nor is there any interval 

 of time between them, till the bodies which are to divide have already acquired 

 the shapes of polypi. 



The clusters of the bulbous sort have an origin entirely different from those of 

 the other sorts of clustering polypi. Yet do these clusters enlarge, and the po- 

 lypi upon them multiply, in the same manner as those of the other species. 



Explanation of the figures in pi. 8, referred to in this paper. — Fig. 7 represents 

 the necessary apparatus, for observing commodiously and regularly a clustering 

 polypus with the microscope. In the glass a, is the end of a peacock's feather, 

 bcf, bent at c, its extremities, by the spring of the feather, being kept close 

 against the sides of the glass. At one of the ends f of the feather one of its 

 beards is left on, which is long enough to fasten to it at m a slip of water horse- 

 tail dl, on which is a polypus, which is by this means kept so close to the side 

 of the glass, as to be within reach of a magnifier of a short focus, such as e. 

 This magnifier is screwed on to a ring whose arm nghas at its extremity g a ball 

 playing in a socket, so as to make a joint; there are again other like joints at h 

 and i, by the help of which the magnifier may be moved every way, and be con- 

 veniently brought near the object. The foot ik is fixed in the board on which 

 the glass is placed. The light of a window in the day-time is sufficient to ob- 

 serve an object so placed within the glass, either with the bare eye, or with a 

 hand magnifier; but if a magnifier of a short focus be necessary, the shutters 

 must be closed, and a wax light must be placed behind the glass, at such a height 

 as to have its light fall directly on the object ; and a magnifier so placed nftiy 

 remain, if there be occasion, for several days in the same posture without any 

 inconvenience. — Fig. 8 exhibits a cluster of polypi, of the first of the 2 species 



