88 THE OCEANIC HYDROZOA. 



sometimes the shortest, so as to suggest that here, as in other Physophoridee, the youngest 

 organs are nearest the proximal end of the body. Some of these organs were lanceolate and 

 compressed at the base, others obliquely truncated at the base, and rounded at the apex. Five 

 or six lines of thread-cells ornamented their outer surface, and each contained a narrow canal 

 which nearly reached its apex, and was not ciliated. The hydrophyllia could be raised 

 and depressed, and the animal could propel itself by alternating these movements. 



There were twenty to forty hydrophyllia, but never more than eight polypites. 



Irregular cavities occur in the walls of the latter organs, which Kolliker considers to be 

 glandular. 



A series of hydrocysts (Fiihler), some fourteen or twenty in number, and always more 

 numerous than the pol)rpites, are attached by short peduncles around the margins of the 

 hydrosoma. Their walls are muscular and ciliated internally and externally, and their apices 

 are surrounded by thread-cells. 



There is a tentacle for each polype, whose general structure appears to be very similar 

 to what 1 have described above, but there is a good deal of apparent difference in the sacculi 

 and their appendages. 



Kolliker says — "The saccculi (nesselknopfe) consist of many parts. Their pedicle 

 divides into two organs; a stalked, elongated capsule, and a crescentic, proper urticating cord 

 (nesselstrang); to whose extremity two prehensile filaments (fang-fiiden) and a pyriform vesicle 

 are attached. All of these parts are hollow, and contain the same clear liquid as the stem. 

 The urticating cord shows the ordinary structure. First, large thread-cells, one of which 

 is shown with its thread projected in fig. 10; then smaller thread-cells, inserted in rows 

 in the thickened wall, between which a reddish-brown pigment is deposited. Finally, 

 there are two muscular cords in the concave part of the organ. The prehensile filaments 

 are thread-like, short, and very contractile, so that they can shrink into a very small 

 space, and are beset throughout with small thread-cells ; while on the other hand, 

 the pyriform sac appears clear, and although quite similar in form and position 

 to the analogous organ in Agalniopsis Sarsii, exhibits no movements and is not ciliated. 

 The stalked elongated capsule, lastly, exhibits in its walls, and, as it would seem, also, 

 in its interior, a beautiful reticulation, in whose spaces, besides a clear fluid, yellowish 

 or reddish fatty-looking globules are often contained. Besides, the yellow middle part 

 is (though not always) surrounded by transverse fibres, and, at one point, covered with 

 dark organs like urticating organs, and drops of fat. The signification of this vesicle, which, 

 like the other parts, was observed colourless, especially among the uppermost of these organs, 

 is altogether doubtful. In the younger and youngest sacculi, such as were frequently to be 

 observed at the root of the tentacles, it w-as not unusually closely applied to the concave side 

 of the urticating cord, but I could find no close relation between the two parts, nor did 

 it seem that the capsule took any share in the movements of the urticating cord, for, indeed, 

 it exhibited none itself." 



On comparing this description and its accompanying figures with my own notes 

 and drawings, I entertain no doubt that the structure of the tentacles in the two 

 Anihoryhim is essentially the same ; that, in fact, the " stalked elongated capsule " is the 

 involucrum ; the " urticating cord" the sacculus ; the pyriform sac the dilated median lobe ; 

 and the "small tentacles" the filaments. 



