5$ TILE VOYAGE OF H.M.S. CHALLENGER. 



suffered from having been pressed closely one against the other in the same bottle, 

 so that they are flattened, and the relief of the body surface rendered indistinct. The 

 dimensions given above and the following description of the form of the body are therefore 

 merely of hypothetic value ; the unfavourable state of preservation also explains why I 

 have omitted to give exact numbers in describing the different parts of the body. 



The height of the body in the living animal seems to have been small, its breadth 

 essentially greater in the region of the oral disk than at the base, so that the whole form 

 of the body may be termed " dish-shaped." It is divided into an upper broader and a 

 lower narrower section by a deep circular constriction. Nearly one hundred tentacles, 

 probably of astonishing length, hang down from the margin of the oral disk. In the 

 smallest specimen there was still one tentacle which extended into a thin filament, 8 cm. 

 long. I grant that this measurement may have resulted from the tentacle having been 

 forcibly stretched, but considering that the diameter of the animal itself only amounts to 

 l'O cm., we may safely assume that the length of the tentacles exceeds the former several 

 times. This is also perhaps the reason why the tentacles are nearly all torn away. 

 Whether the tentacles of each different order are of equal size or not, can only be deter- 

 mined by examination of other specimens. 



The surface of the wall (fig. 1) is marked by about one hundred longitudinal furrows, 

 which lie at ecpial distances from one another, correspond to the origins of the septa, 

 and pass as radial streaks on to the pedal disk. Besides these longitudinal furrows, 

 horizontal furrows run in the upper fourth close under the corona of tentacles, parallel 

 to the margin of the oral disk ; the swellings between the circular furrows are broadest 

 above, whilst they become narrower and flatter below. The swellings and furrows 

 are more pronounced on the endodermal side than on the ectodermal ; at the same time 

 w T e see in longitudinal section (fig. 6), that the internal furrows correspond to the external 

 swellings and vice versa, so that the wall is pleated transversely. Its substance is, more- 

 over, partially thickened, and it is on account of these partial thickenings that the swell- 

 ings project more towards the inside than towards the outside. 



The thickening and pleating of the wall are caused by the mesodermal circular muscle, 

 whose bundles of fibrillse are arranged close under the endoderm in layers, which run 

 parallel to the surface and follow all its pleatings. There are from nine to ten such 

 layers inside the uppermost and broadest swelling (fig. 6, a) ; they gradually decrease in 

 number, in the middle (fig. 6, fi) there are only about four, and later (fig. 6, 7) only two, 

 till finally the circular muscle extends a little way in the now flat part of the wall as 

 a single layer of small bundles which continue to become more sparse (fig. 6, S). The 

 separate muscular fibrillas are remarkably thick, whilst the bundles formed by them are 

 small, and as usual compressed in the direction of the longitudinal axis of the animal. 

 The smallest bundles lie immediately below the epithelium, from which they appear to 

 be formed, as shown in figs. 7, a, /3. 



