CHAPTER IX 



PORIFERA {CONTINUED) : REPRODUCTION, SEXUAL AND ASEXUAL- 

 PHYSIOLOGY DISTRIBUTION FLINTS 



The reproductive processes of Sponges are of such great import- 

 ance in leading us to a true conception of the nature of a sponge 

 that we propose to treat them here in a special section. Both 

 sexual and asexual methods are common ; the multiplication of 

 oscula we do not regard as an act of reproduction (p. 174). 



Fig. 111. A, amphiblastula larva of Sycon raphanus ; B, later stage, showing invagina- 

 tion of the flagellated cells, c.s, Segmentation cavity ; ec, ectoderm ; en, endoderm. 

 (After F. E. Sclmlze, from Balfour.) 



A cursory glance at a collection of sponge larvae from 

 different groups would suggest the conclusion . that they art 

 divisible into two wholly distinct types. One of these is th< 

 amphiblastula, and the other the parenchymula. This was the 

 conclusion accepted by zoologists not long ago. We are indebted 

 to Delage, Maas, and Minchin for dispelling it, and showing that 



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