the Sponges to the Corals. 205 



thing equivalent to Hackel's hypothetical Protascus, and from 

 which the existing stock of sponges and corals has probably 

 been evolved (and it must not be forgotten, by the way, that 

 the latter and by far the more highly organized of the two 

 stocks had attained the very zenith of its development long 

 before the epoch referred to had commenced its decline), it 

 nevertheless foi-ces itself upon one's mind that the evidence 

 he brings forward in support of the supposed intimate relation- 

 ship of the two groups as they now exist is based rather on 

 affinities of analogy than of homology. 



By the corals, as a matter of course, and in concurrence 

 with Hackel's own rendering, is understood that section of 

 the Cojlenterata known as the Zoantharia or Anthozoa, which 

 forms them. Hackel, after some time spent on the examina- 

 tion of the calcareous sponges (" Calcispongi^ "), essays to 

 demonstrate that the whole group of the sponges is far more 

 closely allied to that of the Zoantharia than most modern natu- 

 ralists have been inclined to allow, and that this particular sec- 

 tion contains an existing form, Prosycum (Hack.), Avhich, de- 

 rived from the hypothetical Protascus, may be regarded as the 

 stock-form from which all the other Calcispongias have been 

 evolved. 



This last hypothesis seems possible, and even highly pro- 

 bable ; and we must not omit here to ])ay a willing tribute 

 of admiration to the valuable contribution to science and the 

 vast amount of original information Ernst Hackel's recent 

 researches have been productive of, and this relative to a 

 group of the Spongiadse which up to the present time had been 

 looked upon as very sparingly represented, but which his 

 zealous investigations have resulted in augmenting to no fewer 

 than 42 genera and 132 species. At the same time, however, 

 the arguments he advances in seeking to demonstrate the 

 close relationship of the Spongiad^ and Actinaria seem scarcely 

 sufficient to warrant his proposed amalgamation of the two 

 groups as sections of the same subkingdom — many of these 

 arguments, moreover, being purely theoretical, and entirely in- 

 consistent with the facts which have been elucidated by the 

 investigations of other experienced naturalists. 



In accordance with the opinion in the first place conceived 

 by Leuckart, Hackel looks upon an aggregation of coral- 

 animals, or polyp-colony, as the equivalent of a sponge-mass 

 with its large " water-canals " opening outwardly ; he, how- 

 ever, carries his supposition of existing homologies between 

 the two organisms to a far greater extent than the first-named 

 writer ever attempted to attain to. 



Maintaining, in confirmation of tlie theory propounded by 



