154 ARTHROPODA. 



1. Into what parts does the body seem to be divided? Do 

 all of these parts show segmentation? 



2. Find the following organs. 



(a) The stalked, prominent eyes. 



(b) The antennce. In the female the first are slender and 

 the second vestigial. In the male the first are slender and the 

 second are enormously enlarged to form a clasping organ. 



(c) The labrum (not an appendage) forms an upper lip. 



(d) The mandibles, beneath the labrum and by the sides of 

 the mouth. Do they have cutting-edges? 



(e) Vestigial maxillae behind the mouth. 



(/) Swimming appendages. How many are there? Notice 

 the fringe of hairs on each. What are these for? Remove one 

 and examine it with a microscope. The lobes have been des- 

 cribed as exopodite and endopodite, but their exact relation- 

 ship is not certain. 



A drawing is desirable. 



DAPHNIA. 



This small fresh-water form frequently occurs in large num- 

 bers in small pools and brooks. Determine how it swims. Being 

 small and transparent, it may be satisfactorily studied with a 

 compound microscope. 



1. Notice the shape and extent of the protective covering. 

 To what part of other crustaceans does this correspond? Are 

 the appendages and the abdomen capable of being thrust out? 

 Are there any signs of segmentation of the body? 



2. Determine what parts are used in keeping a current of 

 water passing through the shell. Why is such a current needed ? 



3. If the animal carries young, notice how they are kept in 

 the brood chamber by a spine that extends up from the dorsal 

 portion of the base of the abdomen. 



4. Notice the beating of the heart. 



5. Examine the appendages. 



(a) Are the eyes stalked or sessile? They frequently show a 

 peculiar reaction to light. If the light is cut off from the micro- 



