100 ANNELIDA 



2. The iniddle region consists of five somites. The first, 

 the eleventh segment, is marked by the great pair of wings 

 which are used to bring food to the mouth. Their dorsal sur- 

 faces are grooved and supplied with cilia, as is the median 

 dorsal line. Hence a current of water passes continually to- 

 ward the mouth. The twelfth somite is marked by a dorsal 

 and a ventral sucker, which are modified parapodia. Somites 

 thirteen, fourteen, and fifteen carry notopodial folds or fans, 

 for keeping up a stream of water through the tube. Their 

 neuropodia are mere knobs. 



3. The posterior region is less highly modified. Of how 

 many segments does it consist? Notice their gradual diminu- 

 tion in size. Homologize the parts of their appendages. 



4. The living Chaetopterus contains a green coloring mat- 

 ter and is very luminescent. 



5. The eggs are orange yellow and the sperm milky 

 white. Determine their location. The sexes are separate. 



A drawing is desirable. 



Lillie: Observations and Experiments Concerning the Elementary Phe- 

 nomena of Embryonic Development in Chaetopterus. Jour. Exp. 



Zool., 3, 1906. 



AMPHITRITE ORNATA 



This belongs to the family Terebellidae and lives under 

 stones, or in mud or sand, along shore in stout muddy tubes. 



1. Find the prostomium, which forms an upper lip and 

 bears a transverse group of long, retractile tentacles. 



2. The peristomium, forms the under lip, but bears no ap- 

 pendages. 



3. Find three pairs of racemose gills. These are modifi- 

 cations of the dorsal cirri. 



4. Notice again the feeble development of the parapodia 

 and the absence of ventral cirri and neuropodial setae. Setae 

 are not found posteriorly. Exactly which segments have 



setae? 



5. Find the ventral shield glands which are concerned in 

 building the tube. How many are there? 



