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PROCEEDINGS OF THE 



[Dec, 1857. 



system in the smaller embryo, were reduced to nothing more than 

 the tubular junction of the circulatory canals. The ambulacral 

 tubes, as in the case just mentioned, appeared to be continued 

 upward to the sense-capsule at the superior pole of the animal, 

 and here the singular oblong, asymmetrically placed area, figured 

 by Agassiz in adult Beroids, and which was present, also, in the 

 still younger stage, figured pi. 11, fig. 4, o, of this volume, was 

 very distinct, and was bounded by two sets of double outlines, 

 parallel to each other, which would be the appearance of a canal, 

 or vessel, lined internally by a distinct membrane. 



The tentacula of these specimens were all capable of being 

 more or less stretched out after the little animal in the manner of 

 Pleurobrachia, as figured by Agassiz. Indeed, they have, about 

 this stage, the same form of tentaculum as in that genus, that is, 

 a main lash, very extensile, from which depend more or less nu- 

 merous lateral threads. Their motion in the water was lively, 

 but, nevertheless, slow, on account of the small number of ciliary 

 blades in proportion to the size of the embryo; nevertheless, they 

 trail their tentacula more or less after them, even in these very 

 young stages. 



After these dates I took numbers of these embryos in various 

 stages, and with the ambulacral tubes, exhibiting various degrees 

 of descent towards the mouth. They were usually pyriform, but 

 in one instance an almost spherical shape was exhibited, posses- 

 sing, however, like the pyriform specimens, the two labial appen- 

 dages, representing the lobes of the adult. The tubes which, in 

 the adult, are prolonged to border the lobes, had, in this specimen, 

 anastomosed, already forming thus two loops, one on each side of 

 the mouth. The gastric tubes, also, which are the first to reach 

 the mouth, had here begun giving off at right angles, one on each 

 side of their inferior extremities a short ramus, which, no doubt, 

 was designed to form the circular tube around the mouth, and 

 eventually to connect themselves with the prolongations of the 

 superficial tubes. The details of the development, so far as the 

 remaining tubes are concerned, which distribute themselves in a 

 tortuous manner, two on each of the lobes, have not been, as yet, 

 made out on account of the pressure of other observations. In 

 these specimens, however, the tentacular chambers had made a 

 very decided progress towards the mouth. 



Since the.se observations were taken, I have succeeded in rais- 

 ing genuine Bolina, with its large, graceful lobes, from bi-labiate 



