64 SECOND GENERAL MEETING. 



III. Conchisions. 



The larval development shows that Sponges cannot be con- 

 sidered Ccfilenterates. Such a comparison must start either from 

 the larvffi or the adults. 



If it be based on the larvae, then neither the architecture nor 

 the composition of the adults is in any way comparable. 



If it be based on the adult structure, then the larval development 

 of Sponges is altogether anomalous and not similar to any other 

 known development, since the ectoderm is internal, surrounded 

 completely by the endoderm. 



There are two possible views : 



(i) That the sponge larva is comparable to a Ccelenterate 

 planula, after which point the groups must be supposed to have 

 diverged ; then sponges would be Metazoa, but an independent 

 phylum. 



(2) That no comparison is possible between either the larvae 

 or the adults, but sponges are to be regarded as independently 

 developed from Choanoflagellata. 



The latter view is most jarobable. In favour of it : 



{a) In the adult, the remarkable collar cells, not known else- 

 where except in Choanoflagellata. When those cells are not func- 

 tional their collars are retracted. 



{b) In the larva, a blastula stage at first directly comparable 

 to a Choanoflagellate colony composed of (a) collar cells in which 

 the nutrition is in abeyance, and consequently the collars are with- 

 drawn, (yS) reproductive cells. 



All the tissues of the sponge arise, by a series of modifications 

 from (a), those which are least modified becoming the collar cells 

 of the adult. 



The discussion was continued by Professor Dr Ernst Haeckel, 

 who was followed by Dr VOSMAER, who said : — 



Mr President, Ladies and Gentlemen, — Some time ago I was 

 requested by the Subjects Sub-committee to take part in the dis- 

 cussion about the question of the position of Sponges in the 

 Animal Kingdom. It was my firm intention to decline this request 

 for reasons which will soon be obvious to you. If I, nevertheless, 

 claim your attention, it is only because some of my friends insisted 

 that I should give my opinion in the matter. 



The chief reason that I first declined, is simply this, that I am 

 thoroughly convinced that it is not possible to say more than — zve 

 do not know. 



I am afraid it is not very pleasant for those who are not 

 especially interested in Sponges to hear a man, who is more or 

 less a specialist, proclaim his ignorance ; but I beg you to believe 

 that it is still less pleasant for himself 



I think we may safely say that Sponges do NOT belong to the 



