278 



CRUSTACEANS. 



principal segments bearing three large and pointed spines, which have their edges 

 armed like the blades of a saw. Very different is Andania, which is one of the 

 largest of amphipods, reaching a length of 2 inches. Many members of the group 



construct tubular dwelling-places, in 

 which they take shelter, and lay their 

 eggs. For instance, the British Am- 

 phitha rubricata, which is a brilliant 

 crimson colour, builds a nest of particles 

 of seaweed cemented together with 

 threads; while another species of the 

 same genus (A. littorhia) makes a tube 

 by cementing together the edges of a 

 leaf of growing weed, so as to make 

 a tube open at both ends. Again, 

 according to Bates, Podoacerus capil- 

 latus " builds its nest in a very bird- 

 like manner in submarine forests ; the 

 nests consist chiefly of fine thread-like 

 material, woven and interlaced, being 

 established firmly in the branches of 

 zoophytes ; some small extraneous frag- 

 ments are often bound with it, but these 

 intention. The form of the nest is 

 These nests are evidently 



gigantic andania, Andania gigantea (nat. size). 



appear more the result of accident than 



somewhat oval, the entrance being invariably at the top 



used as places of refuge." 



In the tribe Caprellina the head has coalesced with the first segment of the 

 thorax, and the abdomen is reduced in size, with most 

 of its appendages wanting. The two principal families 

 are the Caprellidai, or skeleton -shrimps, and the 

 Cyamidce, or whale-lice. In the former the thorax is 

 cylindrical, and the abdomen, with its limbs, rud- 

 imentary. In the typical Caprella the third and 

 fourth thoracic segments are without legs, but bear a 

 pair of branchial vesicles ; the appendages of the 

 second pair are developed into claspers, and those of 

 the three last pairs are of the ambulatory type. 

 These shrimps seldom swim, but climb amongst the 

 branches of seaweeds and zoophytes. When at rest, 

 they grasp the stems of the weeds with their hind- 

 limbs, and, holding the body in an erect position, wave 

 their long antennae in search of prey. In the whale- 

 lice, which live parasitically upon cetaceans, the short 

 and conical head is united to the first segment of the 

 thorax, which consists of six free, flattened segments. 



As in Caprella, the third and fourth segments of the body bear no limbs, but are 

 furnished with a pair of gills, usually turned over the animal's back. In the 



skeleton-shrimp (somewhat 



enlarged). 



