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 larvse, but develope at once into the hydraform condition of 

 the parent. 



The figs. 1-6 of plate 19 represent Sertularia thiiia. The 20th 

 plate is dedicated to the PedicelUna, 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. nulcms=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 tentucula discernible. 



" At this stage the PedicelUna 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 hydrcE, 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 TuhMlaria 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 TniTicELLA^^ftra, 



