178 PROGRESS OF MICROSCOPICAL SCIENCE. 



criticism passed on Dr. Gray's " Classification " is as just as it is 

 severe. After a description of the methods of examination, the author 

 proceeds to give a detailed account of the anatomy and nat iral 

 history of the calcareous sponges, and this occupies the greater part 

 of the first volume. The second is devoted to a detailed description 

 of the whole group in systematic order, with diagnosis of species and 

 ample synonomy. The plates in the third volume, drawn by Professor 

 Hackel with the camera lucida, are admirably exact, though artistic 

 effect is sometimes sacrificed to a somewhat diagrammatic clearness. 

 They remind one of the excellent illustrations of Bronn's 

 " Thierreich." The class of spouges is divided into Fibrospongice, 

 including most of Grant's and Bowerbank's silicious and ceratose 

 genera, Myxospongice, represented by Halisarca and Calcispongice vel 

 Grantice. This third class contains three families, Ascones (Leucoso- 

 lenia Bowerbank), Leucones (Leuconia Bowerbank), and Sycones 

 (Grantia Bowerbank), represented by Ascetta, Leucetta and Sycetta 

 respectively. The genera are chiefly characterized by their spicula. 

 The author agrees with Oscar Schmidt in deducing all known sponges 

 from a single primitive form (Archispongia, Protospongia), which he 

 supposed to have resembled Halisarca more than any other existing 

 genus. He regards the class as very distinct from the Protozoa, and 

 most nearly related to the Ccelenterata, a view with which English 

 readers are familiar from Mr. E. E. Lankester's interesting paper on 

 Zoological Affinities of Sponges in the 'Annals and Magazine of 

 Natural History ' (vol. vi., 1870). Indeed it was the position taken by 

 Leuckart himself in 1854, seven years after the sub-kingdom of 

 Ccelenterata had been established by himself and Frey. If we admit 

 that each sponge-pyramid is not a colony of Protozoa, but a multi- 

 cellular organism, its likeness to a polyp is very striking : the chief 

 differences are the absence of tentacles and of thread-cells. The 

 latter structures, however, kave,"we believe, been detected in some 

 Mediterranean sponges since the publication of Professor Hackel's 

 work. Comparing the " Stammbaum " given at the end of the first 

 volume with that in the third edition of the ' Sckopfungsgeschichte ' 

 (1872), published five months earlier, we find that the author now 

 makes all sponges descend through "Archispongia," and " Protascus" 

 from an equally hypothetical " Gastraea," while the Ccelenterata 

 diverge from Protascus as Archydra. This makes the affinity less 

 close between Myxospongias on the one hand, and between Calci- 

 spongiaj and Coralligena on the other. The modification brings the 

 Stammbaum nearer to the classifications actually used by other 

 zoologists, and is so far an advantage. With regard to nomenclature, 

 Professor Hackel defends the proposal which he made in 1869 to 

 revive the old name of Zoophyta (used by our countryman, Wotton, 

 in 1552) in order to include sponges (or Porifera) and Ccelenterata 

 (or, as he prefers to call them, Acalephre). Admitting the justice of 

 the classification, there seems no sufficient justification for the change 

 of names. 1. Priority belongs to the name given by those who first 

 establish true affinities, and not to vague and fanciful names given 

 two hundred years before Linnams. 2. To say "Zoophyta" is no 



