Chap. IV. PARYPHA CROCEA. 251 



the tentacles are very seldom seen stretched to their fullest extent, but when the 

 Hjdroid is in its native habitat, with the water flowing past it rapidly, they equal 

 in length the whole head, from the base to the mouth, and wave to and fro like 

 slender threads, as if the animal had no control over them. In the various shapes 

 which they assume, in connection with the proboscis, they agree with Thamnocnidia 

 spectabilis and tenella (PI. XXII.). The inner surface (PI. XXIII. Fig. 1% j?) of the 

 proboscis is also ridged longitudinally at the upper part, but at the base these 

 ridges (j>/) anastomose and form a raised network. 



The branch, or peduncle, which carries the medusoids is a hollow, double-walled 

 tube {Figs. 18, 18", 19, 19''). The outer [a) and inner walls {h) are respectively 

 continuous with the outer and inner walls of the proboscis. The outer wall («) 

 is thin and very transparent, and the inner Avail {Fig. 19, b) is about three times 

 as thick as the outer one. The cavity of the peduncle is in direct communication 

 with the stomach, and in it a current of chymiferous fluid and granules is con- 

 stantly passing backward and forward in the same way as occurs in the main 

 part of the body. The same degree of sensibility and contractility obtains here 

 as in the tentacles, and also the same flexibility under the influence of flowing 

 water. Each branch is a single uniform stem, from the tip to the base, or very 

 near it, as it sometimes happens that two branches arise from a short and thick 

 single trunk. The pedicels to which the medusoids {Fig. l*", a, b, c) are attached 

 are either single {a, b) or once (c') or twice {e) branched. At the tip of each 

 branchlet a medusoid is attached. When the medusoids are most crowded, the 

 whole mass is so dense as to hide the proboscis entirely, except at the extreme 

 tip, allowing just room enough for the buccal tentacles to move and the mouth 

 to open. When the head is held upright, with the mouth uppermost {Fig. 1*), 

 the bunches of medusoids hang down between the tentacles {f-) of the lower 

 series ; but when the axis of the head trends horizontally {Fig. 1°), then the 

 bunches (c) are pendent between the tentacles of the lower side ; and if the. head 

 hangs with the mouth downward, the proboscis is embraced by these pedulous 

 bunches. When, however, the tide is flowing in or out very fast, then every 

 thing is stretched out in the direction of the swift current. The Larger tentacles 

 {t) at the base of the head are as numerous, and have the same general form, 

 as those of the upper row, when seen with the naked eye ; and are tapering 

 from the base to the tip, where they terminate bluntly. When observed closely, 

 with the aid of a lens, it is easy to perceive that they are not cylindrical, but foui*- 

 sided, so that in a transverse section (PL XXIIP. Fig. 3) we have the upper {a) and 

 lower («') surfaces flat, and narrower than the lateral {c^) flat or slightly concave 

 sides. The proportions in the breadth of the upper and lower to the lateral 

 surfaces vary gradually from the base to the tip of the tentacle ; at the base 



