THE STOMAPODA 



209 



they still retain the name of Shrimps at that place, and are only called " Prawns " when they acquire 

 larger dimensions. 



Calocarls macandrce (Bell). This little Crustacean, which is found living at a depth of nearly 

 two hundred fathoms, is fossorial in its habits, burrowing in sandy mud. Its eyes are quite rudimen- 

 tary, being destitute both of pigment and cornea. Many Crustaceans obtained from great depths in 

 the Swiss lakes prove to be blind. This is also the case with several species of Crustacea met with in 

 the great Mammoth Cave and in the caverns of Camiola and Adelsberg. 



Dr. A. S. Packard has described a Cray-fish, named Cambarus pellucidits, an Amphipod 

 (Niphargus stygius), and two Tsopods (Titanetlies albus and Ccecidotea stygia), from the Mammoth 

 Cave, Kentucky, all of which are blind. " The eyes," says Dr. Packard, " in Cambarus, are 

 rudimentary in the adult, but are larger in the young. This is evidence that the embryo 

 develops like those of other species, and that the inheritance of blindness is probably due to 

 causes first acting on the adults and transmitted to their young until the production of offspring 

 that become blind becomes a habit." 



Both Niphargus and Cranyonyx, two forms of Gainmaridce, have been obtained in. England 

 from wells and pumps in the Chalk and Oolite formations. They are wholly or partially blind. 



Taking 

 Those 



CHAPTER III. 

 CRUSTACEA (concluded). 



STOJfAPonA Squilla Mysis ISOPODA Bathynomus Tanais The ' ' Gribble " A sellus Arcturus Sphceroma Parasitic 

 Forms AMPHIPODA The "Sand-hopper" Orchestia and other Forms Aberrant Amphipods XIPHOSURA King 

 Crabs Character Habits EURYPTERIDA TRILOBITA PHYLLOPODA Character CLADOCERA OSTRACODA 

 COPEPODA Parasitic Forms CIRBIPEDIA RHIZOCEPHALA BALANID^ LEPADID^E Barnacles. 



ORDER II. STOMAPODA (MOUTH-FOOTED). 



IN the STOMAPODA we find a considerable divergence from the DECAPODA already noticed. 

 Squilla as an example, the segments are much less coalesced than in the Lobster, 

 bearing the eyes and antennules are readily separated from the front 

 of the head, and are not covered by the carapace, which only conceals 

 eight segments, whereas in the Lobster it extends over fourteen. The 

 gills are no longer attached to the thoracic appendages, and enclosed in 

 a branchial chamber formed by the head-shield, but they are transferred 

 from the thoracic limbs to the abdominal swimming-feet, and are free 

 and uncovered.* The first thoracic appendages are developed into a 

 pair of robust claws, the terminal joint being furnished with a row of 

 long and sharp re-curved teeth, which can be doubled back upon the 

 penultimate joint, which has a groove to receive it like a pocket-comb. 

 Armed with these two innocent-looking toilet requisites, Squilla goes 

 about seeking whom he may devour. 



In another genus belonging to this order (Mysis, or the " Opossum 

 Shrimp," Fig. 30) special branchise seem to be absent, their duty being 

 performed by the series of flabelliforai appendages attached to Jw pedi- 

 palps, or thoracic feet, certain of which are modified in the female to 

 form a " pouch," or marsupium, in which the eggs are protected and the 

 young retained whilst passing through their earlier stages of existence. 



These Opossum Shrimps are frequently met with in countless myriads 

 towards the surface of the Greenland Sea, and, small though they be, 

 they form the chief part of the food of the Common Whale (Balcena 

 mysticetus), by which such a quantity of fat is accumulated. It seems at first sight incredible that 

 so large an animal can be supported on so slender a repast, but, as in eating Whitebait, numbers 

 must count, and doubtless the Whale devours many hundreds of thousands at each mouthful. 



* Hence they might aptly be termed naked-giUed. Crustacea. 

 265 



Fig. 29. SQUILLA MANTIS. 



