544 Records of the Indian Museum. [Vor. XI, 
was sessile or rested upon the basal bulb (pl. xxx, fig. 1). In such 
cases the hydranths measured 0'15 mm. to 0'27 mm. in length, and 
their greatest diameter varied from 0°14 to 0°2I mm. 
The following table showing the dimensions of various represen- 
tative polyps gives at the same time an idea of the progressive 
development of an individual, the relative age or developmental stage 
being approximately indicated by the number of tentacles, All 
the polyps, with the exception of the first, were collected at the 
same place and time, and were killed under identical conditions. 
The measurements are in millimetres. 
DIMENSIONS OF ANNULELLA GEMMATA. 
Stalk-like 
prolongation. Basal Bulb. 
Tentacles. Polyp. 
| 
| >See TT & 
| | 
| 
| | | 
| 
| . . 
Maximum] Total | Maximum 
| Number. f Length. | 
| : 
Diame- Bent Horizontal 
length. | length. | diameter. ter. Pt" | diameter. 
| 
| —-— ~ — = —_—- 
4 O'17 a7 Vil sin ag none o'04 | orl 
| ‘o8 
5 O13 O'15 O'rI4 none Soe 
| no perisarc 
6 o'44 0°63 o'16 0°35 Orr! broken. 
8 0°75 0°84 | O'21 O°42 orl Orls Over 
9 1°46 O81 0°25 0°35 0°17 O13 O15 
12 1°38 0°98 0°28 0°46 O14. o'2 0°25 
Tentacles. 
The tentacles are confined to a somewhat prominent median 
zone on the hydranth. Over this they are irregularly scattered, 
at least three or four distinct levels being recognisable. Their 
number varies from 4 and 5 on the youngest individuals observed 
to 12 in the largest, but the average seems to centre about 6. 
The appearance of the tentacles is characteristic and beauti- 
ful. They bear throughout their length, at fairly close and 
regular intervals, batteries of cnidoblasts aggregated in large 
projecting rings, or globular masses which resemble beads strung 
upon the axis of the tentacle (see pl. xxxa, fig. 7). These rings or 
elobes have a diameter averaging three times that of the tentacle 
proper. Between the larger batteries there are occasionally smaller 
clumps of cnidoblasts in narrow rings or tiny circular groups. 
A globular battery terminates each tentacle, but since its size does 
not much exceed that of the cnidoblast rings the capitate condition 
is not always very evident, especially in contracted tentacles. 
The detailed structure of the tentacles was examined in serial 
sections (see pl. xxxa, fig. 8). The typical cell-layers are repre- 
