REVIEWS. 17 



species upon which they are found, than has hitherto been supposed. It may, 

 for instance, be the case, that those furnished with those offensive weapons live 

 upon a kind of food different from that of the others, who do not require such 

 an aid in the capture or weakening of their prey. The Polyzoa may, perhaps, 

 be thus divided into vegetable and animal feeders ; or into feeders upon the dead 

 and those which subsist upon living organisms. One thing, however, may be 

 affirmed, that these organs afford, in many cases, excellent and available syste- 

 matic characters, of which application this Catalogue will afford abundant evi- 

 dence. With respect to this part of the subject it will be, therefore, unneces- 

 sary here to add more than a few words. 



u Of the two sets of organs the Avicularia are found by far the most extensively ; 

 existing, in fact, in the majority of genera constituting the cheilostomatous 

 Polyzoa. In applying these appendages for the purposes of classification, it is 

 necessary to divide them into three classes 1, the pedunculate ; 2, the sessile ; 

 3, the immersed. The two latter classes, however, run insensibly into each other, 

 while the pedunculate form is obviously quite distinct, inasmuch as it presents an 

 additional feature in the shape of a basal joint. It is to this form of Avicularian 

 that the term ' bird's 1 or % vulture's heads' is more properly applied. It occurs 

 in Bugula avicularia, B. plumosa, B.flabellata, B. dentata^ and Bicellaria ciliata; 

 while it is wanting altogether in Bugula neritina, Bicellaria grandis, and B. 

 gracilis species, therefore, which it is very desirable should be examined in the 

 fresh or living state, for the purpose of examining whether the inhabitant of the 

 cell does not afford characters sufficient to cause these species to be referred to 

 genera distinct from those to which, from consideration of their skeletons alone, 

 they are now regarded as belonging. A modification of pedunculate Avicularian, 

 where it assumes the form of a long, trumpet-shaped, or ' iufundibuliform' organ, 

 exists in Bicellaria tuba ; with the exception of this latter organ the pedunculate 

 Avicularia are always placed on the anterior surface of the cell, on one side, below 

 the level of the aperture. 



" The sessile form of Avicularian, distinguished from the immersed, occurs pretty 

 extensively, though not so abundantly as the latter form. With a single excep- 

 tion, Amastigia nuda is almost invariably placed upon the front of the cell, below 

 the aperture, as in Alysidium Lafontii, most species of the genera Meniphea, 

 Scrupocellaria, and Canda, and in many of the genus Cabarea in some (as in 

 Scrupocellaria ferox) attaining gigantic dimensions. It is distinguished from the 

 immersed form of Avicularia, not only by its greater projection, but also, and, per- 

 haps, more essentially, by its being composed of a more or less flexible material ; 

 while in the latter form, where it is even somewhat prominent, the cup is always 

 calcareous and rigid. 



"The immersed form of the Avicularian occurs in a great number of genera and 

 species, and, in many instances as in the genus Lepralia affords excellent specific 

 characters. The variety of appearances and position afforded by this form of Avi- 

 cularian will be best appreciated upon inspection of the figures." 



We have extracted these observations at full length, with the hope of 

 engaging the eyes of many who have already, perhaps, barely noticed these 

 curious appendages ; and, we trust, that a Catalogue, drawn up with such 

 care and fidelity, will soon prove its utility by increased exertions on the 

 part of many a solitary student, who, without such aids and encourage- 

 ments, would be almost tempted to abandon, as fruitless, the field of 

 research he had marked out. Two points in the Catalogue we notice with 

 regret one the frequent change of nomenclature, in some instances dif- 

 ferent even from that recently adopted in the " List of British Radiata," 

 another publication of the British Museum Trustees ; in extenuation of this, 



VOL. II. B 



