330 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



Here he follows the results gained by this author " in die 

 letzten Konsequenzen hinein," and proves his theory for the first 

 time in a decided manner. 



He, in the first place, drew attention to the homology between 

 the ciliated cavity of the simple Calcispongiae (Grantise), and the 

 gastral cavity of a Hydroid Polyp. He compai-ed the mouths 

 of these two with one another, and he dwelt on the accessory 

 difference between them ; that in the one case tentacles surround 

 the mouth whilst the other has no arms. The pores of the 

 Sponges he compares with the numerous cases of waterholes in 

 the Ccelenterata. (1.) 



" Allerdings," Leucart continues : — " Sind nun nicht alle 

 Poiiferen so einfach organisirt, wie die Kalksckwamme, vielmehr 

 ist die Mehrzahl derselben mit eniem Hohlensystem versehen, 

 welches mit der weiten Leibeshohle der Grantien und Syconen 

 nur geringe ^Ehnlichkeit hat, allein es ist zur Geniige beckannt, 

 dass der coelenterische Apparat auch soust durch peripherische 

 Ausstiilpungen und Verastelungen die mannigfachsten Formen 

 annimmt." 



In these words nearly everything is contained that concerns the 

 comparison between the morphological structure of the Sponges 

 and the Coelenterata ; only that these ideas can be further worked 

 out and that a few words can be added about the Ontogenesis and 

 Phylogeny of these two large groups. 



Balfour (2) is inclined to consider the Sponges as a type of 

 Metazoa developed separately for itself from the Protozoa. And 

 this appears to him to be proved by the following facts : — (1.) By 

 the peculiar structure of the free larvae ; (2.) By the early 

 development of the Mesoblast in the Sponges, and particularly 

 (3) by the remarkable structure of the digestive canals. 



As far as the first reason is concerned, I am not inclined to 

 consider it as sufficiently general ; the remarkable pecularities of 



(1.) Haeckel, who, extraordinary to say, did not know Lenkart's deduc- 

 tions, compares six years later the Sponges and Acalephes in nearly the 

 same manner. Kalkschwiimme. Band I. Seite 462, M.A.O. 



(2.} Balfour. A Manual of comparative Embryology, Vol. II., p. 309. 



