NATURE AND AFFINITIES OF THE SPONGES. 149 



disciples of the doctrine of evolution, a far more fascinating interpretation 

 of the structure and relationship of these organisms. 



The following year, that of 1869, was signalized in the annals of the 

 scientific world by the publication of Professor Ernst Haeckel's brilliant 

 disquisition in the 'Jenaische Zeitschrift,' Bd. v. 1869 (reprinted in the 

 'Annals' for January and February, 1870), in which this talented author 

 announced, in the most emphatic terms, that the sponges were more nearly 

 related to the corals, or Anthozoarian Ccelenterata, than to any other 

 organized beings, and that the position hitherto assigned to them among the 

 Protozoa was fallacious, and could no longer be maintained. Practically, 

 in the advancement of this theory, Haeckel may be said to have merely 

 resuscitated and clothed in a new and attractive garb the moribund one 

 that, first originating with Ellis and Pallas, was still more extensively 

 developed by Leuckart, but rejected by the verdict of subsequent in- 

 vestigators. This supposed affinity, as advocated by Leuckart and his 

 predecessors, was, however, one only of broad external isomorphic or homo- 

 plastic resemblances. In accordance with their views, each efferent or 

 oscular area in a compound sponge-body was regarded as the equivalent 

 of an individual polyp of a coral stock, minus in each instance the 

 characteristic tentacles, stomachal sac, and internal mesenteries and septa 

 that distinguish the representatives of the corals. Summing it up, such a 

 likeness as evoked by Leuckart on the part of the sponges with respect to 

 the corals may, borrowing a dramatic simile, be aptly compared to the 

 play of ' Hamlet,' minus the king of Denmark. Professor Haeckel, how- 

 ever, disinterring and infusing new breath into Leuckart's abandoned con- 

 ception, claimed for it a far wider and more deeply reaching significance. 

 It was insisted upon by the illustrious biologist of Jena that not only a 

 general external or homoplastic resemblance existed between the organic 

 groups in question, but that the internal structure and histological organiza- 

 tion of the two also coincided. Following out this line of argument, it was 

 represented that the nutritive canal system of the sponges was both homo- 

 logous and analogous with the gastrovascular system of the corals ; that 

 both the corals and the sponges were characterized by the possession of 

 similar distinct external and internal cellular layers, or ectoderm and 

 entoderm ; and that the adult organisms were derived in either case from 

 similar primitive diploplastic ciliated larvae, planulce and gastrulce, these 

 again being developed from ordinary segmented ova. 



As may have been anticipated, this bold conception of Professor 

 Haeckel's inaugurated for the sponges an era of most close and rigid 

 investigation not yet ended, which has already resulted in a mass of 

 evidence that has added vastly to our previous knowledge of the ultimate 

 composition of these structures. None of this testimony, however, can be 

 said to confirm precisely that interpretation of the structural or develop- 

 mental phenomena insisted upon by Haeckel. In the majority of instances, 

 indeed, it is entirely subversive of his theory. Among the earliest of 



