Bibliographical Notices. 393 
only partially successful, but it appears that the ova, after their dis- 
charge from the external and naked bulbules, do not enter into me- 
dusiform larvee, but develope at once into the hydraform condition of 
the parent. 
The figs. 1-6 of plate 19 represent Sertularia thuia. The 20th 
plate is dedicated to the Pedicellina, but the figures tell less of its 
structure than do those of Hassall and Van Beneden. We may 
quote the general description of the species (P. nutans=P. gracilis, 
Sars), which is also applicable to P. echinata, not distinguished from 
the preceding by our author. “ In an early stage it appears as a white 
globular head, crowning a short stem, one scarcely half a line high. 
When more advanced, it generally occurs, or, perhaps, more readily 
attracts notice, when in numerous colonies of individuals rising about 
a line and a half. Then it consists of a smooth white stem, crowned 
by a variable campanulate hydra, with fourteen ciliated tentacula. 
The stem of certain specimens has appeared prickly, sometimes in- 
vested by foreign matter; and I have thought a web uniting the 
roots of the tentacula discernibie. 
«« At this stage the Pedicellina generally dwells in numerous so- 
cieties, implanted on the twigs of other zoophytes, or distributed 
profusely over shells. 
“The adult rises half an inch in height by a smooth bare stem, 
- with twenty or a greater number of hydre, meagrely and irregularly 
disposed on branches or pedicles to right and left, on one or on both 
sides. But such luxuriance is very rare. Among a multitude of 
specimens I have seldom found any with even a few animals. 
“It is only in early stages, when the hydra is solitary, that it can 
be most satisfactorily inspected. Then, the head is discovered to be 
of an extremely variable shape, frequently distorted in an uncommon 
manner, —such as I have not seen in any other zoophyte,—and next 
restored to its symmetry. Sometimes it is flattened, or it is preter- 
naturally enlarged on one side, swollen, contracted, or otherwise, at 
the will of the animal ; and always presenting considerable diversity of 
aspect, either by one or by the various specimens of a colony.” (p. 60.) 
The author notices a singular habit in the species. He says, “‘'Though 
quiescence always prevails during the earlier part of the day, among 
a colony of single animals, that is, those consisting of only a head 
and stem, all are observed in motion as the hours advance, and as 
the sun begins to decline. The tentacula closing over the mouth, 
the heads become globular, nod, and strike against each other, which 
they are enabled to do by flexibility of the stalk. Where many are 
arranged in a row, they seem literally to pass a blow along the whole 
line, as if in sport. Singular it is, that all animals, even the hum- 
blest, seem to have moments happier than others of their existence ; 
and testify, by unequivocal demonstration, their present enjoyments 
in conscious security.’ (p. 62. 
Sir John goes on to describe Tubularia sultana = Fredericella sul- 
tana, and Avenella fusca, a hitherto unnoticed ascidian zoophyte para- 
sitical on other zoophytes, &c. These species are figured in the first 
volume. Another new ascidian zoophyte he names Trrriceria flava, 
