108 ANNELIDA 



studied. Observe 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 pushing 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 exten- 

 sively developed in some species as to hide the prostomium 

 entirely. 



3. Identify eight setigerous somites anteriorly, in which 

 the capillary setae are in the notopodium and the uncini, or 

 hooked setae, are in the neuropodium. With the peristomium 

 they form a "thorax" of nine somites. In the somites which 

 follow (the "abdomen") observe that the uncini and the capil- 

 lary setae stand in the reverse order. How do you interpret 

 the above fact? 



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

 fecal groove) divides them into pairs toward the posterior 

 end of the worm. 



A drawing is desirable. 



HYDROIDES 



This is a member of the family Serpulidae. Study living 

 specimens and their heavy calcareous tubes. Notice the 

 banded branchiae (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. 

 Okada: Remarks on the Reversible Asymmetry in the Opercula of 



the Polychaete Hydroides. Jour. Mar. Biol. Assoc. Unit. Kingd., 18, 



1933. 

 Shearer: On the Development and Structure of the Trochophore of 



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



