CALCAREOUS SPONGES. 717 



In 1891 von Lendenfeld proposed ^^Baodification of Haeckel's 

 "natural" system, retaining only two genera, Ascetta and 

 Ascandra, the former genus lacking oxea, the latter possessing 

 them. 



In the same year Dendy, in his " Monograph of the Victorian 

 Oalcarea Homoccela," while accepting Polejaeff's conclusion that 

 only a single genus could be recognised, proposed to divide that 

 genus into sections and subsections, according to the type of 

 colony formation and canal system. Three sections were re- 

 cognised, Simplicia, Reticulata and Radiata, and the Retictdata 

 were further subdivided into Indivisa and Suhdivisa, according to 

 the absence or presence of an endogastric network. Of these 

 sections the Radiata now constitute the genus Dendya of Bidder, 

 while the other two are of little value to the systematist. 



In 1896 Minchin proposed to distinguish three genera of 

 Homoccela, Glathrina, Leucosolenia and Ascandra, and in 1900, 

 in Lankester's 'Text-Book of Zoology,' he recognised two distinct 

 families, Clatlmnida? and Leucosoleniidee, and gave (p. 110) the 

 following classification and diagnosis : — 



"Grade A. HOMOCCELA, Pol., s. Ascones, H. 



" Gastral layer continuous. 



"Family 1. Clathrinid^e, Minchin. Porm reticulate. Tri- 

 radiate systems always present, equiangular ; monaxons present 

 or absent. Collar-cells with nucleus at base. Larva a parenchy- 

 mula. Genera — Clath7-ina,Grcij (=^ Ascetta, H., pars, Ascaltis, H., 

 pars, etc., and Leucascus, D.) ; Figs. 2, 6, 7, 8 ; Ascandra, H., 

 emend. { = Homandra, Ldf., for Ascandra falcata, H.) ; Dendya, 

 Bidder, for Clathrina trijjodifera, Crtr. Family 2. Leuco- 

 soLENiiDiE, Minchin. Form erect ; monaxons always present ; 

 trii'adiates, if present, alate ; collar-cells with nucleus apical ; 

 larva an amphiblastula. Genera — Ascyssa, H. ; Leucosolenia, 

 Bwk. ( = Ascandra, H., pars, etc.) ; Figs. 3, 4, 5." 



In 1909, Zool. Anzeiger, xxxv. p. 280, in response to criticisms 

 by Hammer [1908] and Dendy as to the position of the nucleus 

 in the collared cells, he emended his diagnoses as follows : — 



" Class Calcarba. Sponges with the skeleton composed of 

 calcite, in the form of spicules either monaxon, triradiate or 

 quadriradiate in form. 



" Grade 1. Homoccela. Calcarea with the gastral layer of collar- 

 cells continuous, not forming separate flagellated chambers. 



" Family 1. Clathrinidje. Oscular tubes generally short, 

 arising as shallow vents from the network of tubes, form of the 

 body typically reticulate, Triradiate spicules always present, 

 equiangular, and with the crystalline optic axis vertical to the 

 facial plane of the rays ; monaxon spicules present or absent. 

 Collar-cells with the flagellum arising cjuite independently of the 



