The Lobster. 63 



The front pair are very small and the hind pair very 

 large, but the others are nearly the same size. 



These appendages are all used in swimming when the 

 lobster is young, so are called swimmerets or little swim- 

 mers. In the breeding season the female carries her 

 eggs glued to the small swimmerets. 



Those who have seen a live lobster try to get away in a 

 hurry, know why the sixth pair of swimmerets are eo large. 

 Their broad lobes spread out on each side of the telson 

 in such a way as to make a powerful tail fin with which 

 the lobster strikes the water, thus sending himself forcibly 

 backward. 



We examine the third pair of swimmerets, and find that 

 they consist of a stem (Fig. 2, A") bearing two flattened 

 lobes (Fig. 2, A^ and A3). 



Some of the elaaa will donbtless observe that the second, third, 

 fourth, and fifth pain of swimmerets are all made on the same plan, 

 bat it is not wise to foroe any aneh eompariaoo upon grammar 

 school pnpils. When they are older it will be a part of their work 

 to trace one common plan in all its variations through the whole 

 series of appendages, bat sncfa study of homologies is for maturer 

 pnpils than onrs. 



Fig. 2. — Third segment of the abdomen with its pair of ap- 

 pendages. 



Lesson II. 



In order to give the class a correct idea of all the appendagea, 

 we make blackboard sketches of the month-parts (Fig. 3), and 

 also sew the month-parts, the antennae, and the eyestalks to a piece 

 of dark-colored pasteboard. 



Seview of Lesson I, — The lobster is dark green, with reddish 

 claws. It is tnbnlar in shape. Its skeleton is a hard crnst. The 

 body is in two parts, — the head-thorax and the abdomen. The 

 head-thorax is covered by a great shield called the carapace. The 

 lobster has many pairs of jointed appendages. The abdomen has 

 six rings and a flat telson. There are six pairs of swimmerets on the 



