366 Royal Society. 



branches go on without interruption, and independently of the rest. 

 It appears from a passage which the author has quoted from Cavolini, 

 that he had noticed the circumstance of currents existing in the inte- 

 rior of Sertularie, but had not detected their continuation into the 

 stomachs of the expanded polypi. Similar phenomena, which the au- 

 thor describes in detail, were observed in several Campanularice and 

 PlumularicB ; and several particulars are noticed with regard to the 

 ovaries, and to the movements of the fluids contained in the ova of 

 these zoophytes, before their exclusion from the body of the parent. 

 In some cases, the young polype, after it has attained a certain 

 growth, but while still adhering to the parent, becomes decomposed, 

 and, its substance being absorbed into the body of the latter, it en- 

 tirely disappears. Changes of the same kind frequently take place in 

 different parts of the whole group ; one of the polypes being seen to 

 shrink and gradually disappear, while others shoot forth in more lux- 

 uriant growth, rapidly acquiring a large size. The author regards the 

 circulating fluids in these animals as the great agent both in the ab- 

 sorption and the growth of parts, and throws out the suggestion, 

 that as it flows into the stomach, it may also act as a solvent to the 

 food received into that cavity. The particles which exist in these fluids 

 show their analogy to those in the blood of the higher animals on the 

 one hand, and to those in the sap of vegetables on the other : some 

 appear to be derived from the digested food, and others from the melt- 

 ing down of parts absorbed. In these polypi the author never saw the 

 least appearance of cilia, or of currents in the surrounding water, 

 which are so frequently met with in other tribes of zoophytes. 



The latter part of the paper is occupied by the account which the 

 author gives of his various observations, first, on Ascidice, of which he 

 enters into an anatomical description ; secondly, on the internal cur- 

 rents of water, permeating the branchial sacs, and determined by the 

 vibratory movements of cilia which are seen in those animals ; and, 

 thirdly, on the alternations in the course of the circulation of the 

 blood in the vessels, which at one time flows in one direction, and, 

 after a certain interval, takes the contrary course ; so that the same 

 vessel which at one time performs the function of an artery, performs, 

 at another, that of a vein. This phenomenon of alternate currents, 

 like that in the Sertularia, was met with in every specimen of Ascidite 

 which was examined by the author, and also in a Polyc.linium. 



The paper concludes with several observations on Flustra, from 

 which, as far as relates to the circulation of currents, the author was 

 led to results in many respects analogous to the preceding. 



A paper was then read, entitled, " On the Theory of the Moon." 

 By J. W. Lubbock, Esq., V.P. and Treasurer of the Royal So- 

 ciety. 



The author, adverting to the appearance of M. Plana's admirable 

 work entitled Theorie du Mouvement de la Lune, enters into a com- 

 parison of the analytical methods employed by that author and M. 

 Damoiseau, and points out some differences in the numerical values 

 of the coefficients of some of the arguments in the expression for the 

 true longitude of the moon in terms of her mean longitude. He then 



