368 CONTRIBUTIONS TO THE NATURAL HISTORY 



/. The vertical, funnel-like prolongation of the main cavity of the body. 



/',/". The two forks of that funnel. It should be remarked that the direction of that fork is in the plane of the longest 

 diameter of the circumscribed area, which is also the direction of the longitudinal diameter of the mouth. 



g. The roots of the tentacle. 



h, h^, h-. h designates the whole tentacular apparatus, with all its complicated parts, h^ being the tentacular apparatus 

 of one side, and h- the tentacular apparatus of the opposite side. And these numbers are appropriated to the same ap- 

 paratus in every figure, whatever may be the position in which the animal is observed. It will be noticed that these ten- 

 tacles are placed at right angles with the plane of the mouth and the circumscribed area. 



i. The eight horizontal tubes of the chyraiferous apparatus which reach the vertical tubes, following the vertical 

 combs. In all the figures the horizontal tubes are numbered in the same way, beginning with No 1 and ending with 

 No. 8. Number 1 is assigned to that tube which extends to the vertical comb in sight on the left hand when the mouth 

 is turned upwards and the tentacular apparatus appears symmetrically on the right and on the left ; so that j', i'-, fl, i* 

 are the four horizontal tubes of one half of the body, and i^, fi, P, i^ are the four horizontal tubes of the opposite 

 half. And if the view I have taken of the diameters of these animals is correct, that the longitudinal diameter of the 

 mouth divides the body into symmetrical halves, one right and the other left, the tubes fl to z* are the tubes of the an- 

 terior half of the body, and the tubes jS to i^ are the tubes of the posterior half, and the tubes i^, i', fi, P are the tubes 

 of the left side, and the tubes P to fi are those of the right side, or vice versa, as we can only establish these general rela- 

 tions between the different diameters without determining strictly which is the anterior and which is the posterior edge of 

 the mouth. It is probable, however, that no distinction is intended in the structure of these animals, as they are capable 

 of assuming inverse positions, mouth upwards and mouth downwards, in which case the edges of the mouth appear in an 

 inverse position. 



j indicates the cavity in which the tentacular apparatus is suspended, and to the inner wall of which it is attached. 

 This cavity opens in/, and tiirough this opening the tentacle may be extended ; but it is also capable of such contraction 

 as to be entirely withdrawn within the cavity j. 



f. Opening of the tentacular cavity, through which the tentacle is protruded. 



k. The main stem of the tentacle from which the fringes arise. 



k'. Fringes of the tentacles which arise uniformly upon the same side, the outside of the tentacle, so that they are 

 stretched in opposite directions from the two sides. But this direction is constantly modified in the vatious attitudes and 

 the various degrees of elongation of the tentacles, as these are capable of being twisted upon themselves ; so that the 

 fringes may appear as forming a spiral upon the main stems, or may be stretched in all possible directions, in their more 

 or less extensive elongations. However, at the base they arise strictly in opposite directions. 



I, I. The vertical combs of locomotive fringes, of which there are eight of uniform length in Pleurobrachia, but four 

 longer and four shorter ones in Bolina. These vertical combs are numbered in the same manner as the horizontal tubes 

 which open into the vertical tubes accompanying the combs, and these numbers correspond in the different figures, in the 

 same manner as in the tubes ; V- to l^ being the combs of one extremity, and P to P those of the other extremity, 

 and P, /I, fi, P being the combs of one side, and P to P the combs of the other side. Upon close examination, it will 

 be found that the short combs in Bolina correspond to l^ and P of one side, and to /'' and P of the opposite side, of Pleu- 

 robrachia ; that is to say, the short combs on the right and on the left side of Bolina embrace respectively the tentacular 

 apparatus of the right and of the left side. 



m represents the muscular apparatus surrounding the mouth ; m indicating the radiating fibres through the agency of 

 which the mouth is opened, and jn' the circular fibres which shut it. 



n represents the main vertical muscular bundles, alternating with the vertical rows of combs. Towards the circum- 

 scribed area, these rows assume a more pennate arrangement, which is designated by the letter t. Otiier fibres also 

 diverge around the opening of the cavity containing the tentacular apparatus, and form a sort of constrictor, p. 



0. Pennate bundles of muscular fibres attached to the sides of the vertical rows of combs and penetrating more or less 

 into the substance of the gelatinous mass. 



