±1 



iiiicleaterl syncvtiuni iindiftViontiated into 

 endoderm cells. 



Fig. 19. A section throug-li a ventral mesenteiy in the 

 Slimmer, showing the manner in which ova 

 are formed. <t. A clump of endoderm cells 

 sinking below the surface. h. A nest of 

 young egg-mother cells, r. A stage in which 

 the protoplasm of the cells composing a nest 

 has fused into a single mass, and the number of 

 nuclei is reduced considerably, d . Last stage 

 in which onlv one nucleus, the o-erminal 

 vesicle of the ovum, lemains and the ovum 

 has begun to increase in size. The retractor 

 muscles ]* . Msc. of the mesentery are here 

 seen in transverse section. 



Fig. 20. Transverse section of an anthocodia in the 

 legion of the gonads, showing the six meseii- 

 tei-ies l)earing ova and the two (doisal) mesen- 

 teries which are barren, Dmf. 



Figs. 21, 22,. 2-!. Three types of spicules met with in 

 Aln/otuiini. 



Fi<>-. 24. The voungest stage of colony foiniation that 

 has been found bv ilie author. 



C, Tinlin; ^ i'o.. Printers, r,H, Victorin Stieet, Liveiiool, 



