338 SYNOPTIC COLLECTION. 



Having found twenty pairs of appendages, it is to be 

 inferred that there are twenty segments in the body. 

 These are usually divided into seven abdominal, eight 

 thoracic, and six cephalic. 



In the preparation (No. 829) the nervous system is 

 shown. 



Amphipoda. Gammarus locus ta M. Edw. (No. 830 ; 

 over Section 12 large figures of G. ornatus M. Edw.), like 

 the Amphipods in general, has a body made up of similar 

 segments uncovered by a carapace. The seven abdom- 

 inal segments bear the six pairs of swimming-feet, the 

 eight thoracic (the first one of which is represented only 

 by remnants of its ventral and lateral portions) bear the 

 thoracic legs and maxillipeds. The eyes of Gammarus 

 are sessile or in other words set in the head. Various 

 parts of Gammarus properly labeled are drawn on a large 

 scale in the plate over Section 12. 



Laemodipoda. Caprella (No. 831 ; see also large 

 figures over Section 12) is a remarkable crustacean in 

 appearance when seen running or climbing over algae, 

 hydroids, or starfishes. The body is made mostly of the 

 thoracic region, the abdomen being reduced to a mere 

 tiny knob. The long, slender segments of the body are 

 distinct and so loosely put together at the joints that the 

 animal can double upon itself. At the forward end there 

 are two pairs of antennae, one long and one short, which 

 probably aid in catching food (Gosse). Back of these 

 are two pairs of appendages which are finely adapted for 

 seizing prey ; the last section but one is enlarged, while 

 the terminal section shuts down upon it as the blade of a 

 pocket knife closes into the handle. 



In the middle of the body two pairs of respiratory- 

 organs take the place of feet ; these also form a pouch 

 for the young during the season of oviferation. At the 

 posterior end are three more pairs of long spiked and 

 bladed feet which take hold of objects when the creature 

 is in action. 



