PLATE XX. 



TUBXJLARIA INDIVISA. 



Fig. 



1. A male colony of Tubularia hnlivisa, natural size; a, young individuals which had attached 



themselves to the stems of the adult colony. 



2. A hydranth from a male colony, with its pendulous raceme-like clusters of gonophores, 



magnified. 



3. One of the raceme-like clusters of gonophores from a female colony. The sporosacs, with 



their contents, are seen in various stages of development. Close to the root of the 

 common peduncle the very young sporosac-bucis may be seen in the form of densely 

 aggregated, sac-like diverticula from the tube of the peduncle. As these approach the 

 distal end of the peduncle they are seen to become more and more developed ; the gene- 

 rative plasma surrounding the spadix has become distinct, then this is seen to have 

 thrown off masses which become developed into actinulaj ; the actinute gradually assume 

 their complete form, and at the extreme end of the raceme they are seen fully developed, 

 escaping through an orifice in the summit of the sporosac. 



4. An actinula shoi-tly after liberation. It is figured in the attitude assumed when moving 



from place to place ; the mouth is turned towards the surface^ over which the actinula is 

 ujoving, while some of the long tentacles are bent in the same direction, and are 

 employed as ambulatory organs. 



5. The actinula after it has permanently fixed itself It has developed a stem, thrown out 



hydrorhizal processes of attachment, and excreted a periderm. The endoderm of the stem 

 has already become canalliculated as indicated by distinct longitudinal striae. 



