38'2 ■ PHILOSOPHICAL TRANSACTIONS. [aNNO 1747. 



other like spherical bodies. These last in a few moments again insensibly open; 

 they then lose their spherical form, and put on that of a bell, or of a polypus as 

 perfect and as compleat, as that by the division of which it was formed. This is 

 the manner in which several species, which he observed of clustering polypi, 

 are multiplied: the whole operation is performed by that sort, of which he has 

 spoken in his former paper, in three quarters of an hour or an hour by these 

 others. 



The polypi of this sort are smaller and whiter than those others, which are 

 represented greatly magnified in the above mentioned figures. The cluster 

 which they form rests on a stem easy to be remarked : this stem is fixed to some 

 other body at its lower extremity, and from its other arise branches, making obtuse 

 angles with the stem itself; other branches again set out from these in different 

 places, and from these last other new ones, and so on. At the extremity of each 

 branch may be seen a polypus: and as all these branches are not of an equal length, 

 so neither is every polypus, as in the other species, at the top of the cluster, or 

 at an equal distance from the base of the stem ; but on the contrary, there are 

 here polypi to be discovered at all heights in the cluster. The assemblage of all 

 these branches forms, together with the polypi at the extremities, a very pretty 

 cluster or groupe, much resembling a tuft or a garland of flowers. 



The stem, which carries all the cluster, and every branch in it, is capable of a 

 remarkable sort of motion. Each will contract suddenly when it is touched, or 

 when the glass containing the cluster is moved, and even sometimes when no rea- 

 son is to be perceived for their so contracting fig. Q, a. The stem and the 

 branches contract and shorten, by disposing themselves into spirals, all whose 

 rings nearly touch each other. Every branch is by itself capable of contraction, 

 independently of the rest : though it but rarely happens that any one branch does 

 contract itself quite alone, for commonly in the action of contracting it happens 

 to touch some other branch, and then that other immediately contracts with it. 

 When the main stem, which bears the whole cluster contracts itself, then all the 

 branches of the cluster contract together also; and the whole becomes entirely 

 closed. A moment after, the branches and the stem again extend themselves, 

 and the whole cluster thus recovers its ordinary figure. But when the cluster is 

 considerably advanced, the stem then ceases to contract itself any more. 



This cluster forms itself in the following manner. A single polypus detaching 

 from the cluster, swims about in 'the water till it meets with some {)roper body to 

 fix itself on. It then has a pedicle, but which is not longer than the polypus 

 itself. In the space of 24 hours this stem becomes 8 or Q times as long as it was 

 at the first: and it is this pedicle which is to become the main stem of the new 

 cluster. About a day after the polypus has been thus fixed, it divides itself into 

 2. Ten or 12 hours after, these 2 polypi again divide each into 2 more: they 



