106 Mr. Patterson on the Cydippe Pomiformis. 



sant. Sometimes it is seen rising to the surface of the water with a slow and 

 equable motion, like that of a balloon, then gradually descending, the mouth being 

 retained in its usual erect position. Next ascending with rapidity, and turning 

 the mouth downwards, or revolving on the transverse axis of the body ; and then 

 abandoning all these modes of progression, revolving on its longitudinal axis, 

 the body being vertical, and in this position twirling round and round the vessel. 

 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 ! 



When the movements of the Beroes were thus diversified, it may be imagined 

 they afforded highly pleasing objects for contemplation, especially as they dis- 

 played in the sunshine a splendid iridescence, caused by the action of the cilia in 

 the water. To the various persons whom I met in the ferry-boats, plying between 

 the Corran and Island Magee, their existence had been previously unknown. 

 They seemed to be delighted no less by the novelty than by the beauty of 

 their appearance, and not unfrequently compared the action of the cilia to that 

 of the paddles of a steam-boat. 



The C. Pomiformis, as now described, differs from the C. Pileus in the num- 

 ber and structure of its cilia, the position of the tentacula, the form of their 

 sheaths, the want of colour in the ova, the inconspicuous structure of the nervous 

 system, the existence of a transverse membrane at the anus, and the position in 

 which the body is held when vigorous and unexhausted. I do not include in 

 these distinctive characters the intestinal vessels which convey the fluid to the 

 several bands of cilia, as it is possible that further investigation may prove tbat a 

 somewhat similar arrangement prevails in both.* 



When we contemplate the delicacy of structure displayed by the Beroes, we 

 are prompted to inquire how they escape destruction from the turbulent element 

 in which they live. On this subject Lesson remarks, " On doit supposer qu'ils 

 augmentent leur pesanteur specifique pour se precipiter a une certaine pro- 

 fondeur, la ou la mer est calme, et ou les lames sourdes, se font moins sentir."f 



• Nov. 22, 1838. I have this day, for the first time, had access to the observations and researches 

 of Martens on the Acalepha of the Beroe family, (Memoires de I'Acad. Imp. des Sciences de S. 

 Petersbourg, tome ii. p. 479,) and am glad to find the above opinion confirmed by the authority of 

 that author. In his illustrative plates, drawn from living specimens, the ramiform vessels going out 

 to the bands of cilia are figured in several different species. 



t Annales des Sciences, tome v. p. 243. 



