extended straight forward, and nearly parallel with each other, forming, together with the 

 tentacles attached to them, a close fascicle extending in the same line with the body. As 

 soon as the polypide reaches the aperture of the cell, they spread out from each other; but 

 this takes place in various manners. Sometimes they are bent with the ends only a little 

 out from each other, while otherwise they are nearly parallel (see fig. 3.); sometimes they 

 spread themselves out so widely on each side, that they stand almost diametrically opposite 

 (lig. 4); sometimes they bend themselves with the ends downwards (see fig. 3); sometimes 

 — and this is most usual, and always occurs when the animal is taken out of its tube (fig. 5), 

 they are bent upwards and backwards, and that often so strongly that they describe a nearly 

 semicircular curve, so that the extremities even touch the dorsal side of the polypide's body 

 (fig. 5 & 15). Tliis great mobility of the tentacular arms or lophophore (.so different from 

 what is observed in the other Polyzoa) which appears to be produced at will by the animal, 

 sometimes in one manner and sometimes in another, must certainly, although it always takes 

 place very slowly and with little energy, be brought about by means of auxiliary muscles or 

 muscular tissue. I have however only succeeded in obseiTing very faint traces of anything 

 of the kind. Wlien the animal is gently compressed between 2 glass plates one may observe 

 on each side some very fine fibres (Fig. 1.5, 18, p) passing obliquely over the gullet, proceeding from 

 the ventral side, where the body of the polypide forms on each side a small conical prominence 

 (ibid. 0.0.) which may perhaps be considered as the ventral corners of the lophojjhore, and 

 losing themselves at the root of the tentacular arms. Tliey appear to represent the retractile 

 muscles of the tentacular arms, which produce their- flexion upwards and backwards. It has 

 not been possible for me to discover any distinct trace of any such thin membrane connecting 

 the basis of the tentacles (the so-called calyx) as is found in the fresh-water Polyzoa. As 

 regards the tentacles themselves, they are indeed (fig. 8) of the usual cylindrical form for Po- 

 lyzoa, and are as usual furnished with cilia; but in the living animal they have a very difi'erent 

 appearance from that of the tentacles in the ordinary Polyzoa. While in the latter they are 

 always in the greater part of their length extended straight, forming a regular corona (see 

 tab. 2. fig. 28. & 30. d.) which only slightly changes its form, the end of some one or other 

 of the tentacles being only sometimes bent a little in one direction or another, the tentacles 

 in the Rhabdoplem-a are always bent and curved in the most irregular manner in all directions 

 (fig. 4. 5. 15. 18) so that there can be no question of any regular tentacular corona. The 

 number of these tentacles, which as above mentioned, are attached in a double row along the 

 anteiior side of the tentacular arms, is somewhat various (about 40 on each arm); they are 

 longest about in the middle, and are in this part about '/s of the length of the arm, and di- 

 minish somewhat towards the base, but more towards the extremity, where they are often 

 quite rudimentary. The tentacular arms themselves, each of which at the base on the dorsal 

 side, is furnished with a little fascicle of unusually long cilia attached to a small tubercular 

 prominence (fig. 15. 17. n) are of very considerable length, quite as long as the whole of the 

 rest of the body; of narrow cylindrical form, thickest at the base and tapering regularly to 



