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sion of Porifera calcaria into two main groups : — Homocoela 

 and Heterocoela, and as to there being only one genus which 

 belongs to the former group: — Leucosolenia. The distinction 

 between Homocoela and Heterocoela is certaioly a natural one. 

 But although I also was of opinion that all Homocoela (the 

 family Asconidae of Haeckel) belonged to one genus , I am now 

 bound to say that Bidder might be right in suggesting that 

 Dendy's discoveries necessitate more than one genus. 



The division in groups or types which Dendy makes in the 

 canal system of diiferent Homocoela, is thus merely a distinction 

 between different things and by no means a classification of ge- 

 nera. For in one and the same individual we see sometimes that 

 the older parts have another canal system than the younger 

 portion of the sponge colony. 



After having shown how close the relation is between the ca- 

 nal system of a colony and the manner in which the individual 

 »Ascon-tubes" are united together, the author distinguishes three 

 sections as regards the canal system of Homocoela: — Simplicia, 

 Reticulata and Radiata. 



1. The Simplicia include such simple forms as never form co- 

 lonies and such forms in which the whole colony consists of Ascon- 

 like individuals , which may branch but never form complex ana- 

 stomoses nor give off radial tubes. Hence the individuality of 

 the members of the colony is always fairly well recognisable. 

 Simple individuals as certain forms of Leucosolenia blanca e. g. 

 are not found between the Victorian sponges; but simple colo- 

 nies are seen of L. lucasi Dd. A slight advance in complexity is 

 exhibited by L. stolonifer Dd. as well in mode of branching as, 

 by the comparative thickness of the ground substance, in the 

 canal system. Owing to this thickness of the wall, the pores are 

 no more simple apertures perforating a thin membrane and »prac- 

 tically identical" with the prosopyles. It are rather wide apertu- 

 res , leading into irregular canals, which may branch and which 

 terminate ultimately in the true prosopyles. Thus, true inhalant 

 canals are formed, which in fact are lined by pinacocytes. 



