CALCAREOUS SPONGES. 797 



a " sylleibid " canal system, a character which we do not consider 

 to be of generic importance. 



Wagnerella Merejhoxvski [1878]^ 



Type species W. horealis Merejkowski. 

 An organism originally described as a calcareous sponge, but 

 shewn by Mayer [1879] to be a Heliozoan. 



In addition to the above, an enormous number of subgeneric 

 nancies, both " artificial " and " natural," were proposed by 

 Haeckel in his two works on the group, but the list is sufficiently 

 swollen out Avith discarded generic names, without including 

 subgeneric ones also. 



PHYLOaENY OF THE CALCAREA. 



Our views as to the phylogeny of the Calcarea, elaborated in 

 the foregoing pages, may now be summarised as follows, and 

 illustrated by the accompanying phylogenetic tree. This tree 

 diflers in certain important respects from that published by one 

 of us twenty years ago [Dendy, 1893 A], which is only to be 

 expected Avhen we consider the great advances made in our 

 knowledge of the group in the interval. All the families of the 

 earlier scheme, and the general ideas of their relationships to 

 one another in the main lines of descent, are, however, retained 

 with but little alteration, but we recognise now four additional 

 families of recent Calcarea, the Leucaltidse, the Minchinellidee, 

 the Murrayonidfe and the Lelapiidae, while several genera have 

 had to be transferred from one family to another. 



One of the most important advances in the classification of 

 the group was made by Minchin [1896], in his demonstration 

 that even among the homocoel sponges two types of collared cells 

 are met Avith, with apical and basal nuclei respectively ; a 

 suggestion Avhich was followed up by Bidder [1898], Avho, it will 

 be remembered, proposed to divide, not only the Calcarea, but 

 the whole of the sponges into BASiiirucLEATA and Apinucleata 

 accordingly, or, confining the suggestion to the Calcarea, to 

 diA^de these into Calcaronea with apical, and Calcinea with 

 basal, nuclei. 



We think it quite likely that the latter of these two suggestions 

 will ultimately prove to be thoroughly sound. With regard to 

 the former, however, Ave consider it highly pi-obable that several 

 distinct types of collared cells Avill be sheAvn to exist in the non- 

 calcareous sponges, though as yet Ave have very little information 

 on this point. 



Continuing the observations of Minchin, Ave find that in the 



