Calcispongise in the Animal Kingdom. 243 



the Myxospongia3 ; and it is among these last that the common 

 stock form of all Sponges, the Arcliispongia^ is to be sought*. 



As, owing to the soft natm-e of their bodies, no fossil 

 remains of the extinct Mjxospongiai could be preserved, we 

 must refer, with respect to their organization, to their few 

 living representatives ; and among these Halisarca is at present 

 the only accurately known form. This genus is also recog- 

 nized by O. Schmidt as that which comes nearest to the 

 common stock form of the whole class, his " Frotospongia^'' 

 He remarks (?. c, p. 34), " that the Halisarcinai realize in the 

 simplest manner the scheme of the sponges cannot be dis- 

 puted." Nevertheless I must dispute the truth of this remark. 

 I have examined two different species of Halisarca alive, 

 namely the colourless Halisarca Dujardinii^ on the Nor- 

 wegian coast (in Bergen), and the violet Halisarca lohidaris^ 

 on the coast of Dalmatia (in Lesina). As regards their 

 anatomical characters, I found both to agree essentially with 

 the representation which Lieberkiihn has given of the former. 

 The soft, gelatinous, amorphous body consists of a lump of 

 nucleiferous sarcodine [syncytium)^ and is permeated by 

 branched canals, which are inflated in all parts into numerous 

 spherical or ellipsoidal flagellate chambers (the ciliary appa- 

 ratus, " Wim])er-Apparatej^'' of Lieberkiihn). Consequently 

 the gastro-canal system is constructed on the Leucon type ; 

 and if we remove by acid the calcareous spicules from a 

 Leucon with a racemose system of branching canals {e.g. 

 Leucortis pulvinar), we obtain a sponge-body which, in 

 essential points, resembles Halisarca. 



But both the Leucon type and the Sycon type undoubtedly 

 descend from the simpler Ascon type ; and in accordance with 

 this we must seek also for tlie Halisarcinai a much more 

 simply organized stock form, standing in the same relation to 

 the Ascontes as the Halisarcina3 to the Leucontes. In order 

 to obtain the picture of this liypothetical stock form we need 

 only to remove, by means of acid, the calcareous spicules from 



* Fritz Miiller, whose instructive work ' Fiir Darwin ' has in so 

 high, a degree advanced the comprehension of the causal nexus between 

 ontogeny and phylogeny, in a memoir " On Darivinella aiirea, a Sponge 

 with stelliform horny spicules," expresses the supposition that the cal- 

 cai'eous spicules of the Calcispongi^ on the one hand, and on tlie other 

 the siliceous spicules of the Silicispongia'*, may have originated from 

 a common horny stock form ; the former by the calcification, the latter 

 by the silicification of the original horny spicules (Archiv fiir mikrosk. 

 Anat. 1865, p. 351). Although this hypothesis seems to be in ac- 

 cordance with our assumption above, it is nevertheless incorrect, as in 

 the Calcispongiai the " horny foundation " of the Fibrospongije never 

 occurs. 



16* 



