32 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



Fig. 15. — Hydranths, reproductive calyces and medusae of an unde- 

 scribed species of Eucope, magnified about fifty diameters, from a liYlng 

 specimen. Drawn by W. K. Brooks. 



A. A, A. Hydranths or nutritive zooids. 



B. A reproductive calycle, showing the blastostyle and very young 

 medusa-buds. 



C. An older reproductive calycle, with fully-formed medusiB. 



D. View of the lower or oral surface of a young medusa, a few min- 

 utes after its escape from the reproductive calycle. 



E. Side view of same. 



F. Medusa about an hour older. 



G. Side view of medusa, about thirty-six hours after its escape from 

 the reproductive calycle. 



a. Perisarc. b. Endosarc. c. Tentacles of hydranth. g. Manubrium. 

 h. Body of hydranth. 



a. The vase-shaped, tentaculated, nutritive zooids, or 

 hydranths (Fig. 15, A, A, A). 



b. The branched stem, or hydrocaulus by which they 

 are united to each other, and to a common base, or hydro- 

 rhiza. 



c. The transparent chitinous shell, or perisarc (Fig. 

 15, a) which covers the hydrorhiza, the hydrocaulus, and 

 portions of the hydranths. 



d. Make a sketch of these points, showing also the 

 arrangement of the hydranths upon the hydrocaulus. 



II. Examine a portion of a colony with a higher power, 

 and note : — 



a. The transparent cylindrical sheath of perisarc (Fig. 

 15, a) which is annulated above and sometimes below the 

 points where the hydrocaulus divides. 



h. The coenosarc or fleshy axis (Fig. 15, b) which 

 occupies the cavity of the tube, and is loosely attached at 

 intervals to its inner wall. In favorable specimens it will 

 be seen to consist of three layers. 



1. The outer layer, or ectoderm consists of somewhat 

 transparent cells with large nuclei, and forms the outer 

 surface of the coenosarc. 



