HYDROIDES. SPIRORBIS. 99 



the two irregular rows of small ocelli or eye-spots. Account for 

 the presence of eyes in their position. A pair of short tentacles 

 can be seen by spreading the branchiae aside. 



. 2. Find a collar which is used in smoothing the orifice of the 

 tube. This is a peristomial structure and is so extensively 

 developed in some species as to hide the prostomium entirely. 



3. Identify eight setigerous somites anteriorly, in which 

 the capillary setce are in the notopodium and the uncini are in 

 the neuropodium. With the peristomium they form a ''thorax" 

 of nine somites. In the somites which follow, the ''abdo- 

 men," observe that the uncini and the capillary setae stand in 

 the reverse order. How do you interpret the above fact? 



4. Find the ventral shield-glands. A furrow (sulcus or 

 faecal groove) divides them into pairs toward the posterior end 

 of the worm. 



A drawing is desirable. 



HYDROIDES. 



This is a member of the family Serpuhdae. Study living 

 specimens and their heavy calcareous tubes. Notice the banded 

 branchioB (modified palps) and the dorsally placed operculum, a 

 modified gill filament. Look for "eyes" on the gill filaments. 



When eggs and sperm are mature these animals will shed 

 them immediately upon being removed from their tubes and 

 placed in sea-water. The larvae are typical trochophores. 



A drawing is desirable. 



Hatschek: Entwicklung der Trochophora von Eupomatus uncinatus, 

 Philippi. (Serpula uncinata.) Arb. Zool. Ins., Wien, 6, 1886. 



Shearer: On the Development and Structure of the Trochophore of Hy- 

 droides uncinatus (Eupomatus). Quart. Jour. Mic. Sci., 56, 1911. 



SPIRORBIS. 



This animal is also a member of the family Serpulidse. 

 Specimens are very abundant along the shore, attached to Fucus. 



1. Study the tube and notice the way in which it "parallels" 

 the form of a small snail-shell. 



2. Remove a five specimen from the Fucus on which it grows 



