AURELIA. 35 



never become detached and never show further medusoid 

 structure, (c) Elongated individuals, especially near the out- 

 skirts of the colony, that have rounded tentacles, proboscis, 

 and mouth like those of the reproductive individuals. These 

 sometimes branch and have a habit of bending the head toward 

 the base or even twisting the body into a spiral. They are not 

 distinguishable from the reproductive individual except by 

 shape and the fact they have no gonophores. 



4. Notice that the individuals are connected at the bases 

 by a fleshy layer which is responsible for the deposit already 

 mentioned. 



Make a drawing of each kind of individual. 



HYDROCORALLDMA. 



To this group belong forms that have heavy calcareous exo- 

 skeletons. While material is generally not at hand to study 

 the polyps, it is desirable to study and sketch the characteristic 

 forms of colonies such as Millepora and Stylaster, and to note 

 the difference in the distribution of pores. Later you will see 

 how decidedly these differ from the ordinary stony corals. 



SIPHONOPHORA. 



Examine living or preserved specimens of Physalia, and 

 sketch the type with reference to showing, if possible, the follow- 

 ing structures: (a) pneumatophore, (6) dadylozooids, (c) gastro- 

 zooids, (d) gonodendrons, (e) tentacles. It will be well to refer 

 to a text-book to find the positions and functions of each of 

 these. 

 Bigelow: The Siphonophorae. Mem. Mus. Comp. Zool., Harvard, 38, 1911. 



SCYPHOZOA. 

 AURELIA. 



This form is one of the common jelly-fishes, and is found 

 floating freely in the water. It is frequently washed up on 

 shore. To be appreciated these medusae should be seen as they 

 occur at the surface of the sea, before they have been handled 



