NATURE AND AFFINITIES OF THE SPONGES. 155 



temerity in having dared to call in question the soundness of the suggested 

 Coelenterate affinities of the sponges, with a far more substantial share 

 of the learned professor's attention. " Mr. Saville Kent's attacks " upon 

 his theory are finally summed up as incapable of refutation, since he 

 " neither understands the arguments brought forward, nor is in general 

 sufficiently acquainted with the structure and development of zoophytes 

 and sponges." The endeavour is here made to show that Mr. Saville Kent 

 has since that time devoted his best energies to rectifying the omission in 

 his education pointed out by Professor Haeckel, the outcome of his humble 

 efforts in this direction being, however, scarcely conducive perhaps to the 

 firmer establishment of that authority's hypothesis. The most crushing 

 shafts of Haeckel's sarcasm are undoubtedly directed against an accidental 

 misrendering or misinterpretation, on the author's part, of some of the more 

 abstruse questions of homology and analogy propounded as subsisting 

 between the representatives of the two groups in question. Whatever may 

 have been the error in this direction, the very important and significant fact 

 remains that Professor Haeckel's exposition of the Ccelenterate affinities of 

 the sponges, embodied in his ' Monograph of the Calcispongiae,' is charac- 

 terized by a complete abandonment of that position which he had formerly 

 maintained with so much vehemence, and by a repudiation of that very 

 homology he had formerly insisted on, and which was especially disputed by 

 the present author. In order to make this significant contradiction clear, it 

 is necessary merely to quote and compare Haeckel's oracular utterances of 

 the two respective years 1869 and 1872. In his first notable essay, 'On 

 the Organization of the Sponges and their Relationship to the Corals,' he 

 says : 



" Certain sponges differ from certain corals only by a less degree of histological 

 differentiation, and especially by the want of urticating organs. The most essential 

 peculiarity of the organization of sponges is their nutritive canal system, which is 

 both homologous with, and analogous to, the so-called coelenteric vascular system, or 

 gastrovascular apparatus of the Ccelenterata." 



In his 'Monograph of the Calcispongise,' Bd. i. p. 461, his recantation, 

 modestly interred in an unobtrusive footnote, runs as follows : 



" Whereas the near relation of the sponges to the corals, to which I formerly gave 

 particular prominence, is to be understood only as an analogy, not as an homology, 

 I thought at that time that I found in the radiate structure of the Sycones (Grantia 

 (Sycon) ciliatd) an essential morphological point of comparison with the corals ; but 

 the developmental history of the radial tubes of the Sycones, with which I only 

 became acquainted subsequently, has convinced me that these are not homologous 

 with the perigastric radial chambers of the corals." 



Having abandoned his former line of defence, Professor Haeckel 

 depends mainly, in the monograph now under discussion, upon making 

 good his position with relation to the suggested affinities through the 

 evidence he adduces with respect to the developmental phenomena of the 

 Calcispongiae. The radial aquiferous system of the adult sponge, originally 



