PLATE XVII. 



Cladonema kadiatum, Stauridium productuai. 



Fio. 



1. A colony of Cladonema radiatum, magnified. The drawing has been made from the free 



variety of this hydroid. (See the description of the species, page 358.) 



2. The same, slightly larger than natural size. 



3. Cladonema radialum, a free mature planoblast floating in the water. 



4. The same fixed by its appendages of attachment, and with its marginal tentacles thrown 



back over its umbrella. 



5. A marginal tentacle contracted ; the three appendages terminating in spherical capitula near 



the base of the tentacle are the appendages of attachment, and do not participate in the 

 contraction undergone by the rest of the tentacle and its branches. The ocellus, with its 

 pigment and refracting body, is seen in the enlarged base of the tentacle. 



6. Extremity of one of the nodulated branches of a marginal tentacle slightly contracted. 



7. Origin of the radiating canals as seen from the summit of the umbrella. 



8. Velum showing its great width and its circular and radiating fibrillae. 

 y. Planoblast at the period of its liberation. 



10. Mature planoblast, natural size. 



11. Stauridium jjrodtict urn, a colony magnified. 

 13. The same, natural size. 



