420 Bibliographical Notice. 



invested by a coating of spongin ; but this view is given up as 

 untenable, and, with Schulze, he now confesses himself unable to 

 satisfactorily explain their origin •, but it seems certain that, though 

 not produced by the sponge, these filaments are in some way neces- 

 sary to its existence, and may thus be compared with the zooxan- 

 thella3 or jellow cells frequently found in low forms of marine life. 

 Curiously enough these filaments are, in the author's opinion, inva- 

 riably associated with this genus of sponges and with no other, and 

 they are as abundant in the Australian as in the Mediterranean 

 species. 



The sponges included in the Rpongelida^, or third main group of 

 the Monoceratina, have a reticulate or dendritic skeleton of solid 

 horny fibres without proper spicules, but containing foreign bodies 

 and occasionally entirely replaced by large sand-grains ; sometimes 

 rod- or 8-shaped flesh-spicules are present. The ground-substance 

 or mesoderm is transparent, and the ciliated chambers are large and 

 sac-shaped and do not possess special efferent canals. This group 

 is more nearly allied to the siliceous lEeterorhaphidie of Kidley and 

 Dendy, and includes only five genera, two of which, Si'jmntella and 

 Ifaastia, are new ; the latter is somewhat remarkable in having a 

 layer of minute oval siliceous bodies sheathing the fibre. The 

 generic term Spongelia, Nardo, is pi'eferred by the author to that of 

 Di/sidea, Johnston, on the ground of priority, and our English 

 authors who reiain Johnston's name are blamed for their ignorance 

 of Nardo s works ; but Dr. Lendenfeld does not seem to be aware 

 that Nardo's term was unaccompanied by any description whatever, 

 and is therefore invalid. As stated by Oscar Schmidt, the names 

 given by Nardo must remain as shadows merely, since this author 

 did not live to carry out his intention of describing the forms them- 

 selves ; and though it pleased Oscar Schmidt to adopt some of them 

 subsequently, Spongelia included, this would by no means be suffi- 

 cient to displace the properly constituted term Dysidea proposed by 

 Johnston before 0. Schmidt published anything respecting the 

 bodiless term Spongelia. Dr. Lendenfeld has another reason for 

 preferring Spongelia, equally as valid as its assumed priority, viz. 

 " because Schulze, who for the first time defined the genus in a 

 really scientific manner, used that name." 



In the remaining principal division of Lendenfeld's system, that 

 of the order Hexaceratina, the sponges may have skeletons of jjithed 

 horny fibres, or of horny spicules, or they may be without skeletons 

 at all. They are furnished with large sac shaped ciliated chambers, 

 with simple canals. These sponges are regarded as forming a 

 natural group, most closely allied to the siliceous Hexactinellida ; 

 but, judging from the distinguishing features of the three families 

 which constitute the group, it is diflUcult to perceive in what way 

 they are related to each other or to the Hexactinellida. Thus in 

 the leading family, the Darwinellida?, there are fibres and horny 

 spicules, the next family of the Aplysidaj has fibres only in the 

 skeleton, whilst in the third family of the Halisarcidae tliere are 

 neither fibres nor spicules. 



Perhaps the most peculiar horny sponges are those included in 



