564 Records of the Indian Museum. [VoL. XI, 
A much greater advance in the differentiation of the simple 
basal attachment is exhibited in Myriothela cocksit Vigurs, well 
described by Allman (1876) under the name of Myriothela phrygia. 
In the long-tentacled, free-swimming larval stage, a few days old, 
an increase in the thickness of the ectoderm at the aboral extremity 
is noticeable (Allman, 1876, p. 567). This appears to be due to 
the formation of columnar epithelium (see Allman’s figure 15, 
pl. 56). In any case a sucker-like pad is formed by which the 
larva attaches itself to the substratum (p. 565). At this early 
stage of fixation the aboral ‘‘sucker’’ is similar in appearance, 
structure and function to the pedal discs which have been men- 
tioned above, but new developments soon set in. ‘‘ The proximal 
extremity of the animal becomes bent at right angles to the rest 
of the body so as to form a sort of horizontal, stolon-like foot 
from which small fleshy processes with sucker-like extremities, 
and having a considerable resemblance to claspers, are emitted. 
The function of these processes, however, is very different from 
that of claspers; they serve to attach the animal permanently to 
some solid support, to which they fix themselves by their extremi- 
ties. Along with the stolon-like foot they become clothed with 
perisarc, and the actinula has thus acquired all the essential cha- 
racters of the adult trophosome’’ (Allman, 1876, p. 565). 
There is some general resemblance here to the final result in 
Annulella, for although the perisare-covered ‘‘ foot’’ of the adult 
in Myriothela cocksit is a direct development of the larval basal 
disc, it is almost certain that the original basal bulb of any indivi- 
dual of Annulella follows the same course; but the absence of a 
narrow neck between the stolon-like foot and the hydranth of 
Myriothela, as well as the presence of specialized sucker-like pro- 
cesses, mark it as very distinct from the basal bulb of Annulella. 
Almost as distinct is the perisare-covered basal attachment of 
the Tubularid, Corymorpha; for not only does it bear many an- 
choring processes, but the perisarc is really a portion of that 
which at one time enveloped the whole hydranth and which by a 
process of recession became later confined to the lower section of 
the stem (see Torrey, 1907, p. 279). 
As regards the development of its basal bulb directly from 
the proximal portion of the adult hydranth, and of the special 
development upon the basal bulb of a highly differentiated peri- 
sarc, Annulella stands alone. It seems to me that its closest 
affinity in respect of this organ may be with Tiarella, beyond the 
stage of which, however, it has made considerable advance in 
specialization. It is well to remember, however, that in its phylo- 
genetic origin the basal bulb is undoubtedly a development of the 
much simpler naked basal discs characteristic of a primitive group 
of unattached hydroids. 
BASAL TRANSVERSE FISSION. 
Transverse fission as a means of multiplication in adult hy- 
droids is not unusual, and varies from the separating of a minute 
