66 



SPONGES 



am/ih 





,®a 





sf.c 



n/>A - 



23 





Fio. 56. 



Tlirftc stages in the dovplopiufiiit of a gomiiuilo in S/wngiHa (after Zykotl"). In A the anioebo- 

 cytc's (stutocytes), packed with refrinjjent ^;ranulo!<, are Ix'coininn ag^jrej^ated at one spot, and 

 the pariMichyinal cells round them are takiiit; an ciiitlielial form and secretiiiji an advontitions, 

 chitinous envelope ; still further away, theiuni)hi(iiscsaro bein;; forniwi in scattered cells of the 

 parenchyiua. In /{the statncytes are densely packed and enclosed by the chitinous coat with 

 its secretinj; epithelium ; the aniphidiscs an- now passing Imtween the cells of the latter. In 

 C the ami)hidiscs form a dethdtely arranged coat internal to the secretinj; epithelium, which is 

 now placed on the exterior, and is secretin); a second chitinous envelope e.\t«'rnal to the aniph id i.scs. 

 amph, aniphidiscs ; amiili', a young amphidisc ; i.ch.e, internal, and e.cli.e, external, chitinous 

 envelopes ; iil.ep, glandular epithelium ; ar, oxeote spicules of the sponge; ;x(»-.r, parenchymal 

 cells ; st.c, statocytes or gemmule cells. 



