HYDROZOA HTDEOMEDUS2E. 241 



The latter are arranged usually in the form of a circle round each 

 of the nutritive animals. The polyparia are found in the fossil state 



Fam. Milleporidae. JMillepora L. M. alcicornis L. 

 Fam. Stylasteridae. 



(3) Sub-order: Tubularice (Ocellata). Polyp stocks which are 

 either naked or clothed by a chitinous periderm without cup-shaped 

 hydrothecae surrounding the polyp head. The generative buds 

 arise on the body of the Polyp or on the stock. The Medusce which 

 are set free belong to the genera Oceania, Sarsia, etc., and have 

 ocelli. 



Fam. Clavidae. Polyp stocks with a chitinous periderm. Polyp club-shaped, 

 with scattered, simple, filiform tentacles. The generative buds arise on the 

 Polyp body and for the most part remain sessile. Cord y lop liora Allm. The 

 stock is branched ; there are stolons which grow over external objects. Oval 

 gonophores covered by the perisarc. The animals are dioecious. In fresh 

 water C. lacustris Allm. albicola Kirchp., Elbe, Schleswig. The following 

 are marine genera Clava 0. Fr. Mliller. Allied are the Eudendridee with 

 Eudendriwn ramosnm. L. 



Fam. Hydractinidee. Polyp stocks with flat extended coenenchyma and 

 firm encrusted skeletal excretions. The Polyps are club-shaped, with a circle 

 of simple tentacles. In addition to the latter there are large tentacle-shaped 

 Polypoids (Spiralzooids). Hydractinia van. Ben. The medusoid buds sessile 

 on the proliferous animals, which are without tentacles. H. ecliinata Flem. 

 Podocoryne Sars. (fig. 181). The generative buds are freed as Oceanldce. 

 P. carnea, Sars. 



Fam. Tubularidae. Polyp stocks clothed with a chitinous periderm. The 

 polyps possess a circle of filiform tentacles on the proboscis inside the 

 external circle of tentacles. The generative buds arise between the two circles 

 of tentacles. Tulnlaria L. The hydroid stocks form creeping root-like branches 

 at the bottom, from which arise simple or branched twigs with the terminal 

 polyp heads ; the generative buds are sessile. T. (Thamnocnidia Ag.) coronata 

 Abilg. dioecious. Conjmorpha Sars. The stalk of the solitary polyp is clothed 

 with a gelatinous periderm, attaches itself by root-like processes, and con- 

 tains radial canals which lead into the wide digestive cavity of the Polyp- 

 head. The freed Medusa is bell-shaped, with one marginal tentacle, and 

 bulbous swellings at the end of the other radial canals. C. nutans Sars., C. 

 nana Alder. 



(4) Sub-order: Campanularice (Vesiculata). The chitinous skeletal 

 tubes widen out round the Polyp-head to form cup-like hydrothecse. 

 The Polyp-head, the oral cone (proboscis), and tentacles can be in 

 most cases completely retracted into these hydrothecse. 



The generative buds arise almost regularly on the walls of the 

 proliferous individuals, which have neither mouth nor tentacles. 

 The buds are sometimes sessile, and sometimes become separated off 



16 



