226 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



1. The first of these (z) is longer than it is wide, and 

 its manner of development, as well as a comparison of the 

 female abdomen with that of the male, shows that it is 

 formed by the union of two somites. 



The ovisacs (n) are attached to the sides of this 

 segment, and the apertures of the oviducts indicate the 

 line along which the two originally separate somites have 

 become united. 



2. The three following abdominal somites (/, &, ?) are 

 narrow, and the anal orifice may be seen near the centre of 

 the dorsal surface of the last, which carries a pair of diver- 

 gent segmented styles (w), each of which carries four 

 plumose setae. 



c. Notice the free setose ends of the thoracic append- 

 ages projecting beyond the edges of the free thoracic 

 somites. 



d. Make a sketch of the dorsal surface, showing all 

 these points. 



II. In order to get a satisfactory side or ventral view the 

 animal may be placed upon a glass slide with a small drop 

 of water, and then moved into the desired position with a 

 needle. A small piece of paper should be placed near 

 the specimen to support the cover-glass, which will be 

 necessary for the satisfactory study of this aspect. In a 

 side or ventral view note : 



a. The shell-glands; a pair of convoluted, transparent 

 tubes, one on each side near the middle of the ventral 

 margin of the carapace. 



b. The mouth is upon the median ventral line near the 

 anterior end, and is bounded anteriorly by a projecting 

 labrum. Its posterior margin is formed by a bilobed 

 ridge, the metastoma, which can be satisfactorily made out 

 only in a ventral view. 



