VOL. XLIV.] PHILOSOPHICAL TRANSACTIONS. 381 



it is distinctly seen that this motion, though in general resembling that observed 

 in the others, is not a revolving or rotatory motion : such, for example, is the 

 motion which is noticed in that species of polypi which Mr. Leuwenhoeck has 

 described in the 295th No. of these Trans.* This is one of those insects 

 [animalcula] whose motion is the most to be admired, and it is besides exceed- 

 ingly curious on many other accounts. 



The motion in question is very slow in the clustering polypi, just when they 

 are opening again after their division, and he was greatly mistaken, if it might 

 not then be seen very plainly that this motion is not a rotation. The same re- 

 mark applied to the tunnel-like polypus, and that almost during all the time that 

 it employs in its separation. 



Mr. T. made use of an expedient while he was observing the clustering polypi, 

 by which he was able to retard the quickness of their motion. He poured by 

 little and little a small quantity of spirit of wine into the glass they were kept in. 

 This spirit of wine immediately either abated the velocity of their motion, or 

 took it quite away, according to the quantity of it poured in. That which fol 

 lows both in the one and in the other of these two cases, was of use, and 

 threw light on the present question. Sometimes the spirit of wine forced the 

 polypus entirely to draw in its lips within its body, and at other times even to 

 detach itself entirely from its pedicle. 



Another way to take off the celerity of this motion, is to remove the insects 

 into a water which furnishes them much more sparingly with food ; fasting pro- 

 bably weakens them, and from their weakness arises an abatem^t in the quick- 

 ness of their motions. This last expedient is of use and conveniency for observ- 

 ing this motion while it is slower, for several days consecutively. And after- 

 wards on returning the polypi into water stocked with food for them, the motion 

 will soon be restored to its former briskness. He also remarked in the winter, that 

 cold deadened the motion of the clustering polypi: and these animals in all pro- 

 bability are less voracious, and eat less in winter than they do in summer. When 

 the motion in the clustering polypi has been retarded, either by fasting or by the 

 cold, they become whiter, or of a paler colour than before ; they also then cease 

 to multiply. 



What he here proposed to describe, was the manner in which the clusters are 

 formed of a certain species of polypi, which multiply in the main like those re- 

 presented in the figures of the 474th number of the Phil. Trans, and which differ 

 chiefly from them in the form of their clusters. The polypus, when it is ready to 

 divide, first draws in its lips into the body. It then by degrees puts on a round 

 form, and presently after the little spherical body so formed, divides itself into 2 



• Vol. r, p. 175, of these Abridgments. 



