370 CONTRIBUTIONS TO THE NATURAL HISTORY 



jr. Prolongation of the vertical chjrmiferous tubes extending from the oral extremity of the short rows of locomotive 

 combs to the auricles, and following the inner margin of the latter. 



jr'. The returning tube following the outer margin of the auricles, and anastomosing with tubes from the inner surface 

 of the large lobes, <j>, and also with tubes, v, arising from the margin of the mouth. 



p. Prolongation of the vertical chymiferous tubes, extending from the anal extremity of the long vertical rows of loco- 

 motive combs upon the outer surface of the large lobes. 



p. The same tubes turning upwards and inwards. 



tr. The prolongation of the same tubes upon the inner surface of the large lobe, winding again in an opposite direction, 

 and forming several sigmoid curves. 



r. The extremity of the same tubes extending again downwards parallel with the corresponding tube of the opposite 

 side, both meeting upon the median line in t. From these tubes arises a network of tubes, forming more or less rec- 

 tangular meshes, — perhaps a sort of gill, m, from which arises a recurrent tube, <f>. 



V. Tubes arising along the margin of the mouth from the vertical chymiferous tubes, r, which accompany the main 

 digestive cavity. 



<j>. Recurrent tube arising from the margin of the internal network of vessels which spreads over the inner surface of 

 the large lobes. This tube, following a course parallel to the edge of the large lobes, anastomoses near the base of the 

 auricles with the recurrent chymiferous tubes, n, of the auricles, and the tubes, v, from the margin of the mouth. 



^. Auricles, four in number, corresponding to the short vertical rows of locomotive fringes, and therefore analogous to 

 the vertical rows l^, l^, l^, l^. In accordance with this correspondence, the auricles are respectively marked -x^ , x^, x^i X*- 



^jr. Vibratile ciliee along the auricles. 



o>. Vascular network upon the inner surface of the large lobes. 



Plate I. — Various Attitudes of Pleurobrachia. 



Fig. 1. A specimen in a state of rest, the tentacles hanging loosely downwards partly expanded, partly contracted 

 into irregular tubercles ; the fringes not expanded. The position of the specimen is such as to correspond to Fig. 3 of 

 Plate n. 



Fig. 2. A specimen with the body in nearly the same position, but bending obliquely forwards, the tentacles fully out, 

 the fringes also expanded, except those near the base of one of the tentacles, which are partly contracted. 



Fig. 3. A view similar to that of Fig. 1 ; the body, however, slightly turned upon the corresponding vertical axis, 

 so that the tliree posterior vertical rows of locomotive fringes, which are not observable in Fig. 1, appear through the 

 transparent gelatinous mass. 



Fig. 4. Another view, in which the body has the position of Fig. 1 in Plate II. ; one of the tentacles is contracted, the 

 other fully expanded. 



Fig. 5. View from the oral side of the body, corresponding to Fig. 5 of Plate II. The tentacles fully expanded. 



Fig. 6. A view similar to that of Fig. I ; the body, however, very much elongated, moving forwards, the tentacles 

 fully expanded. 



Fig. 7. A view of the animal with the body also elongated, moving horizontally, the profile corresponding to that of 

 Fig. 4 ; the tentacles stretching at right angles ; one with all the fringes out, bending upon itself, while the other is 

 partly contracted, with only a few of the fringes expanded. 



Fig. 8. A specimen with the body horizontal, the tentacles considerably expanded. This figure corresponds to Fig. 7, 

 where the elongation of the body has ceased. 



Fig. 9. A view of the animal nearly in the same attitude as in Fig. 1, but slightly turned more upon its vertical axis. 

 The tentacles slightly expanded; the fringes drawn in, the extremity of one of the tentacles coiled upon itself. 



Fig. 10. A view from the side opposite to the mouth ; the circumscribed area in the centre, but somewhat bent up- 

 wards, in order to show the branches of all the horizontal chymiferous tubes. The tentacles are in the utmost state of 

 elongation. 



