554 Records of the Indian Museum. [VoL. XI, 
small round nuclei and here and there groups of excretory pro- 
ducts ; the former contains many large nematocysts in process of 
formation, especially in the upper region near the aperture in the 
chitinous investment. It is curious that nematocysts shouid de- 
velop in an enclosed sac the ectoderm of which has no contact 
whatever with the exterior, but a similar condition has been ob- 
served in the hydrorhizal portion of Myriothela cocksit (Hardy, 
1891, p. 512), and of Corymorpha (Torrey, 1907, p. 279), and I 
have noticed it in the case of some gonophores. In Anmnulella the 
history of the layers of the sac (see p. 555) offers a simple explana- 
tion. The walls of the sac are thin and leave a moderate space 
for a central cavity which is in direct communication with the 
coelenteron of the hydranth. 
It is a remarkable fact that in the mature bulb there is no 
direct connection between the ectoderm of the hydranth and that 
of the basal bulb. At the constriction or neck uniting the two, 
the ectodermal layer disappears and the chitinous investment abuts 
against the mesogloea. This may be a preliminary to the severing 
of the neck at the time when the hydranth escapes from its hold- 
fast; as such at any rate it would fall into line with the well- 
defined process which precedes the release of the free-swimming 
sporosacs of species of Dicoryne (see Ashworth and Ritchie, 1915). 
An unusual feature distinguishes the mesogloea of the basal 
bulb. It is continuous with the mesogloea of the hydranth, but 
just beneath the neck and within the aperture of the chitinous shell, 
it forms a very much thickened rim deeper than either endoderm 
or ectoderm. From the proximal margin of this ring the mesogloea 
suddenly tapers away, and throughout the remainder of the bulb 
forms a layer of extreme tenuity. 
The chitinous investment of the basal bulb is of rudely 
spherical form, sometimes greatly modified by its contact with the 
solid substratum. The chitin is of very different densities, but 
the upper portions are always the more solid and deeply tinted. 
Round the small but very definite aperture through which the 
neck of the basal bulb passes there is a thickened ring slightly 
incurved. While the perisarc is well defined in the distal portions 
and there exhibit definite growth lines, in the central area of the 
floor of the bulb it gradually loses its compactness and merges into 
an amorphous gelatinous mass of much greater thickness (pl. xxxa, 
fig. ga). In this mass are included, along with other debris, large 
quantities of diatom skeletons in some of which the protoplasm is 
so well preserved as to indicate that the algae continued to live after . 
their inclusion. This unconsolidated basal area may add to the 
efficiency of the basal bulb as a hold-fast, or may provide for the 
expansion of the perisarc-shell during the growth of the sac within. 
The secretion of perisarc is confined to the basal bulb, at the 
neck of which the chitinous covering ends abruptly. Yet masses 
of gelatinous material containing much debris not only surround 
the bulb but are continued for a short distance on the lower 
exposed portion of the hydranth. 
