32 Mr Patterson on a Species of Beroe 



of the jar to the surface of the water, with a slow and regular 

 movement, resembling that of a balloon, and descend at the 

 same rate of progression. Again they would rise more rapidly, 

 turn the mouth downwards, and descend with equal rapidity. 

 At other times, without rising or falling, they would revolve on 

 the transverse axis of the body, a movement of the reality of 

 which the language of Lamarck implies a doubt. Then aban- 

 doning all these modes of progression, they would revolve on 

 their longitudinal axis, holding the body vertical, and in this 

 position twirl round and round the glass. When the movements 

 of the body are thus varied, how great must be the variety of 

 motion in the cilia by which the body is propelled ! Never for 

 more than a second or two do the cilia cease to vibrate. Even 

 then it is not a total cessation, but a slower and alternate move- 

 ment that is exhibited. The cilia on one or two continuous 

 bands would then remain stationary, while the adjacent ones on 

 either side would move. Then those which had been still would 

 be set in motion, and those which had been moving would re- 

 main still. No regular succession of movement was observed, 

 but some portion of the bands of cilia was kept constantly in 

 motion. Hence it may fairly be inferred that they are organs 

 of respiration as well as of locomotion, and that the term " Pleu- 

 robrachia" applied to them by Fleming, is as applicable as 

 " les Ciliogrades" of Blainville. If water moving in elastic tubes 

 along the base of the cilia be the powder by which they are pro- 

 pelled, it is obvious from the preceding observations, that the 

 animal can direct the water into any particular band, and regu- 

 late at pleasure the celerity of its undulations. 



The tentacula of these animals were, next to the cilia, the most 

 attractive of their parts. These organs were not always appa- 

 rent, but remained inclosed in the body of the animal. Among 

 the first thirty-five beroes taken, two only exhibited the tenta- 

 cula, although subsequent examination shewed that they were 

 not wanting in any individual. They were seldom displayed 

 immediately after the beroes had been taken from the net, nor 

 while the glass vessel in which they were kept was crowded by 

 the number it contained. When, however, not more than five 

 or six were placed there, the tentacula were thrown out to their 

 fullest extent, and were occasionally above six times the longest 



