269 



appearances that presented themselves were traced with a camera- 

 lucida, slid over the eye-piece of the microscope. 



In a specimen of the Tubularia indivisa, when magnified 100 times, 

 a current of particles was seen within the tube, strikingly resembling, 

 in the steadiness and continuity of its stream, the vegetable circula- 

 tion in the Chara. Its general course was parallel to the slightly 

 spiral lines of irregular spots on the tube j on one side flowing from, 

 and on the other towards, the polypus, each current occupying one 

 half of the circumference of the tube. The particles were of various 

 sizes, some very small, others larger, but apparently aggregations of 

 the smaller : a few were nearly globular, but in general they had no 

 regular shape. At the knots, or contracted parts of the tube, slight 

 vortices were observed in the current ; and at the ends of the tube 

 the particles were seen to turn round, and pass over to the other side. 

 Singular fluctuations were also observed in the size of the stomach and 

 of the cavity of the mouth ; the one occasionally enlarging, while the 

 other contracted, as if produced by the passage of a fluid from the one 

 into the other and its subsequent recession, thus distending each alter- 

 nately. This flux and reflux took place regularly at intervals of 80 

 seconds 3 besides which two currents were continually flowing, both 

 in the mouth and stomach ; an outer one in one direction, and an inner 

 one in the opposite direction. 



In all the species of Sertularim examined by the author, currents of 

 particles were observed passing along the soft substance which occu- 

 pies the axis of the stem and branches, and were even seen extending 

 into the substance of the polypi themselves, and traversing the sto- 

 machs belonging to each. Contrary to what happens in the Tubula- 

 ria, the stream does not, in these animals, flow in the same constant 

 direction 3 but after moving towards one part for about a minute or 

 two with considerable velocity, it becomes much slower, and then 

 either stops or exhibits irregular eddies, after which it resumes its 

 motion with the same velocity as before, but in the contrary direc- 

 tion ; and so on alternately, like the ebb and flow of the tide. If the 

 current be designedly obstructed in any part of the stem, those in the 

 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 Sertularice, 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 Cantpanularice 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 3 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 



