82 Fresh-water Biology 



C. ADJUSTMENT STUDIES 



Study 17 

 HIBERNATING DEVICES OF SOME AQUATIC ANIMALS 



Materials needed: Preserved specimens of: 



Cladocerans bearing ephippia with winter eggs. 

 Bryozoans bearing hibernacula. 

 Freshwater sponges bearing hibernacula. 

 Slide mounts to show the lesser details. 



Work Program: 



1. A laboratory examination of the materials provided. 



2. Reading in text Life of Inland Waters, pp. 164-169 and 261-268, and in advanced 



text books of zoology, about the life cycle in these three groups, and in rotifers. 



For Record 



1. Sketch carefully: 



(a) A Cladoceran (Daphnia) with developing ephippium. 



(b) A mature free-floating ephippium containing two winter eggs. 



(c) A spray of skeleton of a Bryozoan (Plumatella) showing receptacles for several 



zooids. 



(d) A hibernaculum of Plumatella showing layers. 



(e) A hibernaculum of Pectinella showing layers and marginal hooks. 



(f) One or more hibernacula of a fresh-water sponge (Spongilla) showing outlet 



tube. 



(g) A hibernaculum of Carterius showing outlet tube. 



(h) Spicules of flesh and hibernaculum of same, highly magnified, 



2. Label these drawings so as to indicate sources and significance of the things seen. 



Study 18 

 REPRODUCTIVE METHODS IN FRESH-WATER MUSSELS 



Materials needed: (A) Living gravid mussels representing the families Spheriidse and 

 Unionidae. 



(B) Microscopic preparations: sections of normal and gravid gills: slide mounts 

 (glochidia, etc.). 



Work Program: 



L A laboratory examination of the above materials. 



2. Reading in the text. Life of Inland Waters, pp. 180-182 and 287-292. 



