HYDROMEDUSAE 313 



When closely contracted the tentacles are little longer than the height of the umbrella, 

 rather stout, and gradually tapering in thickness towards the pointed tip ; they are thickly 

 covered with nematocysts in minute papillae (Plate XVIII, fig. 4). When expanded, 

 the tentacles are several times as long as the height of the umbrella and very thin in the 

 greater part of their length, but in the preserved specimens the proximal part of the 

 tentacles, beyond the basal bulbs, is always stout and conical. The clusters of nema- 

 tocysts in the proximal part of the tentacle form small, rounded warts, closely set; 

 towards the distal part these warts gradually become broader, crescent-shaped, clasping 

 around one half to three-quarters of the circumference of the tentacle, and in the 

 outermost part, near the tip of the tentacle, they form complete transverse bands. There 

 is also a bullet-shaped terminal cluster, slightly expanded. The crescent-shaped clusters 

 are thick in their middle part, tapering towards both sides, and they are wedged in 

 between each other without any definite arrangement. The tentacles are hollow 

 throughout their length (Plate XIX, figs. 8, 11), though in the distal part the central 

 cavity is narrow. Such hollow tentacles with nematocysts in distinct transverse bands, 

 more or less completely surrounding the tentacle, are found in all members of the three 

 families belonging to the Limnomedusae. 



The basal bulbs of the tentacles (Plate XVIII, fig. 4) are large and cylindrical or, in 

 a contracted state, somewhat barrel-shaped, a little longer than broad. They have a 

 smooth surface, and very few nematocysts are found in the superficial layer of the 

 ectoderm ; but in the deeper part of the ectodermal epithelium, close to the supporting 

 lamella, there are numerous nematoblasts (Plate XIX, figs. 8, 10), from which, pre- 

 sumably, the tentacle is continually provided with new nematocysts. The basal bulbs are 

 attached to the margin of the umbrella by a narrow base (Plate XVIII, fig. 4) and do not 

 extend into the substance of the umbrella. 



There is one large, cup-shaped ocellus at the base of each tentacle, on the outer 

 (abaxial) side (Plate XIX, fig. 9). The ocellus is not on the basal bulb itself, but on a 

 special papilla (Plate XIX, fig. 8) wedged in between the basal bulb and the margin of 

 the umbrella (as in Moerisia). This papilla is attached to the wall of the exumbrella 

 and is well above the basal bulb. Inside the ocellar papilla the cavity of the basal bulb 

 forms a hook-like, hollow, endodermal prolongation. 



One large abnormal specimen was found on 11 November 1901. The stomach has 

 only three lobes, but one of these gives rise to two radial canals, making four radial 

 canals in all. Moreover, the manubrium is double, two equally developed mouth tubes 

 issuing from two of the lobes of the stomach. 



Vallentin's notes contain some very interesting observations on the living specimens 

 of Tiaricodon coendeus: "11 November 1898: This species is very easily seen in the 

 water. Radial canals, gonads, manubrium, and tentacles bright blue in colour. The 

 tentacles stream away from the umbrella to an enormous distance. A prominent eye- 

 spot can be easily seen at the base of each tentacle." "30 November 1898: Abundant. 

 The large specimens very attractive. The normal position of this medusa is an upright 

 one in the water, a few inches beneath the calm surface of the sea. It seldom moves, 



