372 CONTRIBUTIONS TO THE NATURAL HISTORY 



Fig. 8. The vertical chymiferous tubes of the tentacular apparatus, in their connection with the main cavity, tlie hori- 

 zontal tubes, and the funnel, are represented in an ideal outline, without any part of the tentacles themselves. 



Fig. 9. One bulb of the vertical funnel seen from its narrow side, to show a ball of fecal matter accumulating near the 

 opening of that cavity. 



Plate IV. 



This plate represents the general appearance of the body of Pleurobrachia enlarged and in various attitudes, and gives 

 also several longitudinal and transverse sections of the body, to bring out more fully the relations between the different 

 parts. 



Fig. 1 represents the animal in the same position as Fig. 3 of Plate II. 



Fig. 2 shows the animal in the same position as Fig. 1 of Plate II. 



Fig. 3 represents it in the same position as Fig. 5 of Plate IT. 



Fig. 4 represents it in the same position as Fig. 4 of Plate II. 



Fig. 5 represents it in the same position as Fig. 2 of Plate II. 



Fig. 6 and 7. These transverse sections correspond to the line A B of Fig. 2, which letters (in this figure) have no 

 reference to the lobes of Bolina and the swellings around the mouth of Pleurolirachia, marked also A and B. 



Fig. 8 represents a vertical section in the position of Fig. 2. 



In all these figures the cavities shaded with black lines are the chymiferous cavities and chymiferous tubes. The main 

 stems are cross-barred wherever they are cut, in the section, and the openings of the chymiferous tubes are also cross-barred. 

 The cavity of the tentacular apparatus is marked in addition by lines of dots. On contrasting Fig. 6 with Fig. 7, it will 

 be perceived that Fig. 6 corresponds to a section across Fig. 2 at A, passing through the upper part of the tentacular ap- 

 paratus ; so that the tentacular cavity forms a crescent-shaped opening around the tentacular apparatus. The lower part 

 of the cavity is marked by dotted lines, as are also the horizontal radiating tubes seen below. In Fig. 7, which is a 

 section corresponding to B of Fig. 2, the lower part of the tentacular cavity is laid open at a point where it is occupied 

 internally only by the tentacle itself, and all the radiating tubes and the fringe of the vertical funnel are in sight. In Fig. 

 8, the digestive cavity and the main cavity of the body, and the whole tentacular apparatus, are laid open by a vertical 

 section, and the position which the tentacular apparatus holds within its cavity is fully displayed. 



Plate V. 



This plate represents various structural details of Pleurobrachia more highly enlarged. 



Fig. 1. Part of a tentacle contracted, and the fringes arising from one side. The two fringes on the opposite side are 

 simply displaced by pressure. 



Fig. 2 represents the structure of the tissue under the vertical chymiferous tubes, where it consists of large, irregular 

 cells, probably an ovary. 



Fig. 3, 4, 5, 6 represent the mouth in various degrees of dilatation, assuming different forms, sometimes quite irregular, 

 as in Fig. 3 and 4 ; sometimes elongated, as in Fig. 5 ; sometimes funnel-shaped, as in Fig. 6. 



Fig. 7. The mouth in this figure is entirely shut, assuming a longitudinal form, which, in its direction, corresponds to 

 the direction of the circumscribed area. 



Fig. 8 represents a small portion of a tentacle greatly enlarged, to show the structure of the main stem and that of 

 the fringes. 



Fig. 9 represents the circumscribed area, the bulb of the eye-speck, and the two bulb-like dilatations of the vertical 

 funnel. 



Fig. 10 represents the bulb of the eye-speck, and the surrounding parts still more enlarged. 



Plate VI. 



Various attitudes of BoHna ahia of the natural size. 



Fig. 1 shows the animal as seen in profile. The two lobes, which are entirely shut, appear on the right and left. 



